cpython/Misc/NEWS

+++++++++++
Python News
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(editors: check NEWS.help for information about editing NEWS using ReST.)

What's New in Python 3.2 Alpha 1?
=================================

*Release date: XX-XXX-XXX*

Core and Builtins
-----------------

- The deprecated PyCObject has been removed.

- Issue #6347: Include inttypes.h as well as stdint.h in pyport.h.
  This fixes a build failure on HP-UX: int32_t and uint32_t are
  defined in inttypes.h instead of stdint.h on that platform.

- Issue #6373: Fixed a SystemError when encoding with the latin-1 codec and
  the 'surrogateescape' error handler, a string which contains unpaired
  surrogates.

- Issue #4856: Remove checks for win NT.

C-API
-----

- The code flags for old __future__ features are now available again.

Library
-------

- Issue #6369: Fix an RLE decompression bug in the binhex module.

- Issue #6344: Fixed a crash of mmap.read() when passed a negative argument.

- The deprecated function string.maketrans has been removed.

Build
-----

- Issue 4601: 'make install' did not set the appropriate permissions on
  directories.

- Issue 5390: Add uninstall icon independent of whether file
  extensions are installed.


What's New in Python 3.1?
=========================

*Release date: 27-June-2009*

Core and Builtins
-----------------

- Issue #6334: Fix bug in range length calculation for ranges with
  large arguments.

- Issue #6329: Fixed iteration for memoryview objects (it was being blocked
  because it wasn't recognized as a sequence).

Library
-------

- Issue #6314: logging.basicConfig() performs extra checks on the "level"
  argument.

- Issue #6274: Fixed possible file descriptors leak in subprocess.py

- Accessing io.StringIO.buffer now raises an AttributeError instead of
  io.UnsupportedOperation.

- Issue #6271: mmap tried to close invalid file handle (-1) when anonymous.
  (On Unix)

- Issue #1202: zipfile module would cause a struct.error when attempting to
  store files with a CRC32 > 2**31-1.

Extension Modules
-----------------

- Issue #5590: Remove unused global variable in pyexpat extension.


What's New in Python 3.1 Release Candidate 2?
=============================================

*Release date: 13-June-2009*

Core and Builtins
-----------------

- Fixed SystemError triggered by "range([], 1, -1)".

- Issue #5924: On Windows, a large PYTHONPATH environment variable
  (more than 255 characters) would be completely ignored.

- Issue #4547: When debugging a very large function, it was not always
  possible to update the lineno attribute of the current frame.

- Issue #5330: C functions called with keyword arguments were not reported by
  the various profiling modules (profile, cProfile). Patch by Hagen F<>rstenau.

Library
-------

- Issue #6258: Support AMD64 in bdist_msi.

- Issue #6195: fixed doctest to no longer try to read 'source' data from
  binary files.

- Issue #5262: Fixed bug in next rollover time computation in
  TimedRotatingFileHandler.

- Issue #6217: The C implementation of io.TextIOWrapper didn't include the
  errors property.  Additionally, the errors and encoding properties of StringIO
  are always None now.

- Issue #6137: The pickle module now translates module names when loading
  or dumping pickles with a 2.x-compatible protocol, in order to make data
  sharing and migration easier. This behaviour can be disabled using the
  new `fix_imports` optional argument.

- Removed the ipaddr module.

- Issue #3613: base64.{encode,decode}string are now called
  base64.{encode,decode}bytes which reflects what type they accept and return.
  The old names are still there as deprecated aliases.

- Issue #5767: Remove sgmlop support from xmlrpc.client.

- Issue #6150: Fix test_unicode on wide-unicode builds.

- Issue #6149: Fix initialization of WeakValueDictionary objects from non-empty
  parameters.

Windows
-------

- Issue #6221: Delete test registry key before running the test.

- Issue #6158: Package Sine-1000Hz-300ms.aif in MSI file.

C-API
-----

- Issue #5735: Python compiled with --with-pydebug should throw an
  ImportError when trying to import modules compiled without
  --with-pydebug, and vice-versa.


Build
-----

- Issue #6154: Make sure the intl library is added to LIBS if needed. Also
  added LIBS to OS X framework builds.

- Issue #5809: Specifying both --enable-framework and --enable-shared is
  an error. Configure now explicity tells you about this.



What's New in Python 3.1 release candidate 1?
=============================================

*Release date: 2009-05-30*

Core and Builtins
-----------------

- Issue #6097: Escape UTF-8 surrogates resulting from mbstocs conversion
  of the command line.

- Issue #6012: Add cleanup support to O& argument parsing.

- Issue #6089: Fixed str.format with certain invalid field specifiers
  that would raise SystemError.

- Issue #5982: staticmethod and classmethod now expose the wrapped
  function with __func__.

- Added support for multiple context managers in the same with-statement.
  Deprecated contextlib.nested() which is no longer needed.

- Issue #5829: complex("1e500") no longer raises OverflowError.  This
  makes it consistent with float("1e500") and interpretation of real
  and imaginary literals.

- Issue #3527: Removed Py_WIN_WIDE_FILENAMES which is not used any more.

- Issue #5994: the marshal module now has docstrings.

- Issue #5981: Fix three minor inf/nan issues in float.fromhex:
  (1) inf and nan strings with trailing whitespace were incorrectly
  rejected;  (2) parsing of strings representing infinities and nans
  was locale aware; and (3) the interpretation of fromhex('-nan')
  didn't match that of float('-nan').

Library
-------

- Issue #4859: Implement PEP 383 for pwd, spwd, and grp.

- smtplib 'login' and 'cram-md5' login are also fixed (see Issue #5259).

- Issue #6121: pydoc now ignores leading and trailing spaces in the
  argument to the 'help' function.

- Issue #6118: urllib.parse.quote_plus ignored the encoding and errors
  arguments for strings with a space in them.

- collections.namedtuple() was not working with the following field
  names:  cls, self, tuple, itemgetter, and property.

- In unittest, using a skipping decorator on a class is now equivalent to
  skipping every test on the class.  The ClassTestSuite class has been removed.

- Issue #6050: Don't fail extracting a directory from a zipfile if
  the directory already exists.

- Issue #1309352: fcntl now converts its third arguments to a C `long` rather
  than an int, which makes some operations possible under 64-bit Linux (e.g.
  DN_MULTISHOT with F_NOTIFY).

- Issue #5761: Add the name of the underlying file to the repr() of various
  IO objects.

- Issue #5259: smtplib plain auth login no longer gives a traceback.  Fix
  by Musashi Tamura, tests by Marcin Bachry.

- Issue #1983: Fix functions taking or returning a process identifier to use
  the dedicated C type ``pid_t`` instead of a C ``int``. Some platforms have
  a process identifier type wider than the standard C integer type.

- Issue #4066: smtplib.SMTP_SSL._get_socket now correctly returns the socket.
  Patch by Farhan Ahmad, test by Marcin Bachry.

- Issue #2116: Weak references and weak dictionaries now support copy()ing and
  deepcopy()ing.

- Issue #1655: Make imaplib IPv6-capable. Patch by Derek Morr.

- Issue #5918: Fix a crash in the parser module.

- Issue #1664: Make nntplib IPv6-capable. Patch by Derek Morr.

- Issue #5006: Better handling of unicode byte-order marks (BOM) in the io
  library. This means, for example, that opening an UTF-16 text file in
  append mode doesn't add a BOM at the end of the file if the file isn't
  empty.

- Issue #4050: inspect.findsource/getsource now raise an IOError if the 'source'
  file is a binary.  Patch by Brodie Rao, tests by Daniel Diniz.  This fix
  corrects a pydoc regression.

- Issue 5955: aifc's close method did not close the file it wrapped,
  now it does.  This also means getfp method now returns the real fp.

Installation
------------

- Issue #6047: fullinstall has been removed because Python 3's executable will
  now be known as python3.

- Lib/smtpd.py is no longer installed as a script.

Extension Modules
-----------------

- Issue #3061: Use wcsftime for time.strftime where available.

- Issue #4873: Fix resource leaks in error cases of pwd and grp.

- Issue #6093: Fix off-by-one error in locale.strxfrm.

- The _functools and _locale modules are now built into the libpython shared
  library instead of as extension modules.

Build
-----

- Issue #3585: Add pkg-config support. It creates a python-2.7.pc file
  and a python3.pc symlink in the $(LIBDIR)/pkgconfig directory. Patch by
  Clinton Roy.

Tests
-----

- Issue 5442: Tests for importlib were not properly skipping case-sensitivity
  tests on darwin even when the OS was installed on a case-sensitive
  filesystem. Also fixed tests that should not be run when
  sys.dont_write_bytecode is true.


What's New in Python 3.1 beta 1?
================================

*Release date: 2009-05-06*

Core and Builtins
-----------------

- Issue #5914: Add new C API function PyOS_string_to_double, and
  deprecate PyOS_ascii_strtod and PyOS_ascii_atof.

- Issue #3382: float.__format__, complex.__format__, and %-formatting
  no longer map 'F' to 'f'. Because of issue #5859 (below), this only
  affects nan -> NAN and inf -> INF.

- Issue #5799: ntpath (ie, os.path on Windows) fully supports UNC pathnames
  in all operations, including splitdrive, split, etc.  splitunc() now issues
  a PendingDeprecation warning.

- Issue #5920: For float.__format__, change the behavior with the
  empty presentation type (that is, not one of 'e', 'f', 'g', or 'n')
  to be like 'g' but with at least one decimal point and with a
  default precision of 12. Previously, the behavior the same but with
  a default precision of 6.  This more closely matches str(), and
  reduces surprises when adding alignment flags to the empty
  presentation type. This also affects the new complex.__format__ in
  the same way.

- Implement PEP 383, Non-decodable Bytes in System Character Interfaces.

- Issue #5890: in subclasses of 'property' the __doc__ attribute was
  shadowed by classtype's, even if it was None.  property now
  inserts the __doc__ into the subclass instance __dict__.

- Issue #4426: The UTF-7 decoder was too strict and didn't accept some legal
  sequences. Patch by Nick Barnes and Victor Stinner.

- Issue #3672: Reject surrogates in utf-8 codec; add surrogatepass error handler.

- Issue #5883: In the io module, the BufferedIOBase and TextIOBase ABCs have
  received a new method, detach().  detach() disconnects the underlying stream
  from the buffer or text IO and returns it.

- Issue #5859: Remove switch from '%f' to '%g'-style formatting for
  floats with absolute value over 1e50.  Also remove length
  restrictions for float formatting: '%.67f' % 12.34 and '%.120e' %
  12.34 no longer raise an exception.

- Issue #1588: Add complex.__format__. For example,
  format(complex(1, 2./3), '.5') now produces a sensible result.

- Issue #5864: Fix empty format code formatting for floats so that it
  never gives more than the requested number of significant digits.

- Issue #5793: Rationalize isdigit / isalpha / tolower, etc. Includes
  new Py_ISDIGIT / Py_ISALPHA / Py_TOLOWER, etc. in pctypes.h.

- Issue #5835: Deprecate PyOS_ascii_formatd.

- Issue #4971: Fix titlecase for characters that are their own
  titlecase, but not their own uppercase.

- Issue #5283: Setting __class__ in __del__ caused a segfault.

- Issue #5816: complex(repr(z)) now recovers z exactly, even when
  z involves nans, infs or negative zeros.

- Issue #3166: Make int -> float conversions correctly rounded.

- Issue #1869 (and many duplicates): make round(x, n) correctly
  rounded for a float x, by using the decimal <-> binary conversions
  from Python/dtoa.c.  As a consequence, (e.g.) round(x, 2) now
  consistently agrees with format(x, '.2f').

- Issue #5787: object.__getattribute__(some_type, "__bases__") segfaulted on
  some builtin types.

- Issue #5772: format(1e100, '<') produces '1e+100', not '1.0e+100'.

- Issue #5515: str.format() type 'n' combined with commas and leading
  zeros no longer gives odd results with ints and floats.

- Implement PEP 378, Format Specifier for Thousands Separator, for
  floats.

- The str function switches to exponential notation at
  1e11, not 1e12.  This avoids printing 13 significant digits in
  situations where only 12 of them are correct.  Example problem
  value: str(1e11 + 0.5).  (This minor issue has existed in 2.x for a
  long time.)

- Issue #1580: On most platforms, use a 'short' float repr: for a
  finite float x, repr(x) now outputs a string based on the shortest
  sequence of decimal digits that rounds to x.  Previous behaviour was
  to output 17 significant digits and then strip trailing zeros.
  Another minor difference is that the new repr switches to
  exponential notation at 1e16 instead of the previous 1e17; this
  avoids misleading output in some cases.

  There's a new sys attribute sys.float_repr_style, which takes
  the value 'short' to indicate that we're using short float repr,
  and 'legacy' if the short float repr isn't available for one
  reason or another.

  The float repr change involves incorporating David Gay's 'perfect
  rounding' code into the Python core (it's in Python/dtoa.c).  As a
  secondary consequence, all string-to-float and float-to-string
  conversions (including all float formatting operations) will be
  correctly rounded on these platforms.

  See issue 1580 discussions for details of platforms for which
  this change does not apply.

- Issue #5759: float() didn't call __float__ on str subclasses.

- The string.maketrans() function is deprecated; there is a new static method
  maketrans() on the bytes and bytearray classes.  This removes confusion about
  the types string.maketrans() is supposed to work with, and mirrors the
  methods available on the str class.

- Issue #2170: refactored xml.dom.minidom.normalize, increasing both
  its clarity and its speed.

- Issue #1113244: Py_XINCREF, Py_DECREF, Py_XDECREF: Add `do { ... } while (0)'
  to avoid compiler warnings.

- Issue #3739: The unicode-internal encoder now reports the number of characters
  consumed like any other encoder (instead of the number of bytes).

Installation
------------

- Issue #5756: Install idle and pydoc with a 3 suffix.

Library
-------

- Issue #5311: bdist_msi can now build packages that do not depend on a
  specific Python version.

- Issue #5150: IDLE's format menu now has an option to strip trailing
  whitespace.

- Issue #5940: distutils.command.build_clib.check_library_list was not doing
  the right type checkings anymore.

- Issue #4875: On win32, ctypes.util.find_library does no longer
  return directories.

- Issue #5142: Add the ability to skip modules while stepping to pdb.

- Issue #1309567: Fix linecache behavior of stripping subdirectories when
  looking for files given by a relative filename.

- Issue #5923: Update the ``turtle`` module to version 1.1, add two new
  turtle demos in Demo/turtle.

- Issue #5692: In :class:`zipfile.Zipfile`, fix wrong path calculation when
  extracting a file to the root directory.

- Issue #5913: os.listdir() should fail for empty path on windows.

- Issue #5084: unpickling now interns the attribute names of pickled objects,
  saving memory and avoiding growth in size of subsequent pickles. Proposal
  and original patch by Jake McGuire.

- The json module now works exclusively with str and not bytes.

- Issue #3959: The ipaddr module has been added to the standard library.
  Contributed by Google.

- Issue #3002: ``shutil.copyfile()`` and ``shutil.copytree()`` now raise an
  error when a named pipe is encountered, rather than blocking infinitely.

- Issue #5857: tokenize.tokenize() now returns named tuples.

- Issue #4305: ctypes should now build again on mipsel-linux-gnu

- Issue #1734234: Massively speedup ``unicodedata.normalize()`` when the
  string is already in normalized form, by performing a quick check beforehand.
  Original patch by Rauli Ruohonen.

- Issue #5853: calling a function of the mimetypes module from several threads
  at once could hit the recursion limit if the mimetypes database hadn't been
  initialized before.

- Issue #5854: Updated __all__ to include some missing names and remove some
  names which should not be exported.

- Issue #3102:  All global symbols that the _ctypes extension defines
  are now prefixed with 'Py' or '_ctypes'.

- Issue #5041: ctypes does now allow pickling wide character.

- Issue #5812: For the two-argument form of the Fraction constructor,
  Fraction(m, n), m and n are permitted to be arbitrary Rational
  instances.

- Issue #5812: Fraction('1e6') is valid: more generally, any string
  that's valid for float() is now valid for Fraction(), with the
  exception of strings representing NaNs and infinities.

- Issue #5734: BufferedRWPair was poorly tested and had several glaring
  bugs. Patch by Brian Quinlan.

- Issue #1161031: fix readwrite select flag handling: POLLPRI now
  results in a handle_expt_event call, not handle_read_event, and POLLERR
  and POLLNVAL now call handle_close, not handle_expt_event.  Also,
  dispatcher now has an 'ignore_log_types' attribute for suppressing
  log messages, which is set to 'warning' by default.

- Issue #2703: SimpleXMLRPCDispatcher.__init__: Provide default values for
  new arguments introduced in 2.5.

- Issue #5828 (Invalid behavior of unicode.lower): Fixed bogus logic in
  makeunicodedata.py and regenerated the Unicode database (This fixes
  u'\u1d79'.lower() == '\x00').

Extension Modules
-----------------

- Issue #5881: Remove old undocumented compatibility interfaces in hashlib and
  pwd.

- Issue #5463: In struct module, remove deprecated float coercion
  for integer type codes: struct.pack('L', 0.3) should now raise
  an error.  The _PY_STRUCT_FLOAT_COERCE constant has been removed.
  The version number has been bumped to 0.3.

- Issue #5359: Readd the Berkley-DB detection code to allow _dbm be built
  using Berkley-DB.

Tests
-----

- Issue #5354: New test support function import_fresh_module() makes
  it easy to import both normal and optimised versions of modules.
  test_heapq and test_warnings have been adjusted to use it, tests for
  other modules with both C and Python implementations in the stdlib
  can be adjusted to use it over time.

- Issue #5837: Certain sequences of calls to set() and unset() for
  support.EnvironmentVarGuard objects restored the environment variables
  incorrectly on __exit__.

C-API
-----

- Issue #5630: A replacement PyCObject API, PyCapsule, has been added.


What's New in Python 3.1 alpha 2?
=================================

*Release date: 2009-4-4*

Core and Builtins
-----------------

- Implement PEP 378, Format Specifier for Thousands Separator, for
  integers.

- Issue #5666: Py_BuildValue's 'c' code should create byte strings.

- Issue #5499: The 'c' code for argument parsing functions now only accepts a
  byte, and the 'C' code only accepts a unicode character.

- Fix a problem in PyErr_NormalizeException that leads to "undetected errors"
  when hitting the recursion limit under certain circumstances.

- Issue #1665206: Remove the last eager import in _warnings.c and make it lazy.

- Fix a segfault when running test_exceptions with coverage, caused by
  insufficient checks in accessors of Exception.__context__.

- Issue #5604: non-ASCII characters in module name passed to
  imp.find_module() were converted to UTF-8 while the path is
  converted to the default filesystem encoding, causing nonsense.

- Issue #5126: str.isprintable() returned False for space characters.

- Issue #4865: On MacOSX /Library/Python/2.7/site-packages is added to
  the end sys.path, for compatibility with the system install of Python.

- Issue #4688: Add a heuristic so that tuples and dicts containing only
  untrackable objects are not tracked by the garbage collector. This can
  reduce the size of collections and therefore the garbage collection overhead
  on long-running programs, depending on their particular use of datatypes.

- Issue #5512: Rewrite PyLong long division algorithm (x_divrem) to
  improve its performance.  Long divisions and remainder operations
  are now between 50% and 150% faster.

- Issue #4258: Make it possible to use base 2**30 instead of base
  2**15 for the internal representation of integers, for performance
  reasons.  Base 2**30 is enabled by default on 64-bit machines.  Add
  --enable-big-digits option to configure, which overrides the
  default.  Add sys.int_info structseq to provide information about
  the internal format.

- Issue #4474: PyUnicode_FromWideChar now converts characters outside
  the BMP to surrogate pairs, on systems with sizeof(wchar_t) == 4
  and sizeof(Py_UNICODE) == 2.

- Issue #5237: Allow auto-numbered fields in str.format(). For
  example: '{} {}'.format(1, 2) == '1 2'.

- Issue #5392: when a very low recursion limit was set, the interpreter would
  abort with a fatal error after the recursion limit was hit twice.

- Issue #3845: In PyRun_SimpleFileExFlags avoid invalid memory access with
  short file names.

Library
-------

- Issue #2625: added missing items() call to the for loop in
  mailbox.MH.get_message().

- Issue #5640: Fix _multibytecodec so that CJK codecs don't repeat
  error substitutions from non-strict codec error callbacks in
  incrementalencoder and StreamWriter.

- Issue #5656: Fix the coverage reporting when running the test suite with
  the -T argument.

- Issue #5647: MutableSet.__iand__() no longer mutates self during iteration.

- Issue #5624: Fix the _winreg module name still used in several modules.

- Issue #5628: Fix io.TextIOWrapper.read() with a unreadable buffer.

- Issue #5619: Multiprocessing children disobey the debug flag and causes
  popups on windows buildbots. Patch applied to work around this issue.

- Issue #5400: Added patch for multiprocessing on netbsd compilation/support

- Issue #5387: Fixed mmap.move crash by integer overflow.

- Issue #5261: Patch multiprocessing's semaphore.c to support context
  manager use: "with multiprocessing.Lock()" works now.

- Issue #5236: Change time.strptime() to only take strings. Didn't work with
  bytes already but the failure was non-obvious.

- Issue #5177: Multiprocessing's SocketListener class now uses
  socket.SO_REUSEADDR on all connections so that the user no longer needs
  to wait 120 seconds for the socket to expire.

- Issue #5595: Fix UnboundedLocalError in ntpath.ismount().

- Issue #1174606: Calling read() without arguments of an unbounded file
  (typically /dev/zero under Unix) could crash the interpreter.

- The max_buffer_size arguments of io.BufferedWriter, io.BufferedRWPair, and
  io.BufferedRandom have been deprecated for removal in Python 3.2.

- Issue #5068: Fixed the tarfile._BZ2Proxy.read() method that would loop
  forever on incomplete input. That caused tarfile.open() to hang when used
  with mode 'r' or 'r:bz2' and a fileobj argument that contained no data or
  partial bzip2 compressed data.

- Issue #2110: Add support for thousands separator and 'n' type
  specifier to Decimal.__format__

- Fix Decimal.__format__ bug that swapped the meanings of the '<' and
  '>' alignment characters.

- The error detection code in FileIO.close() could fail to reflect the `errno`
  value, and report it as -1 instead.

- Issue #5016: FileIO.seekable() could return False if the file position
  was negative when truncated to a C int. Patch by Victor Stinner.

Extension Modules
-----------------

- Issue #5391: mmap now deals exclusively with bytes.

- Issue #5463: In struct module, remove deprecated overflow wrapping
  when packing an integer: struct.pack('=L', -1) now raises
  struct.error instead of returning b'\xff\xff\xff\xff'.  The
  _PY_STRUCT_RANGE_CHECKING and _PY_STRUCT_OVERFLOW_MASKING constants
  have been removed from the struct module.


What's New in Python 3.1 alpha 1
================================

*Release date: 2009-03-07*

Core and Builtins
-----------------

- The io module has been reimplemented in C for speed.

- Give dict views an informative __repr__.

- Issue #5247: Improve error message when unknown format codes are
  used when using str.format() with str, int, and float arguments.

- Issue #5249: time.strftime returned malformed string when format string
  contained non ascii character on windows.

- Issue #4626: compile(), exec(), and eval() ignore the coding cookie if the
  source has already been decoded into str.

- Issue #5186: Reduce hash collisions for objects with no __hash__ method by
  rotating the object pointer by 4 bits to the right.

- Issue #4575: Fix Py_IS_INFINITY macro to work correctly on x87 FPUs:
  it now forces its argument to double before testing for infinity.

- Issue #5137: Make len() correctly raise a TypeError when a __len__ method
  returns a non-number type.

- Issue #5182: Removed memoryview.__str__.

- Issue #1717: Removed builtin cmp() function, dropped tp_compare
  slot, the C API functions PyObject_Compare and PyUnicode_Compare and
  the type definition cmpfunc.  The tp_compare slot has been renamed
  to tp_reserved, and is reserved for future usage.

- Issue #1242657: the __len__() and __length_hint__() calls in several tools
  were suppressing all exceptions.  These include list() and bytearray().

- Issue #4707: round(x, n) now returns an integer if x is an integer.
  Previously it returned a float.

- Issue #4753: By enabling a configure option named '--with-computed-gotos'
  on compilers that support it (notably: gcc, SunPro, icc), the bytecode
  evaluation loop is compiled with a new dispatch mechanism which gives
  speedups of up to 20%, depending on the system, on various benchmarks.

- Issue #4874: Most builtin decoders now reject unicode input.

- Issue #4842: Don't allow trailing 'L' when constructing an integer
  from a string.

- Issue #4991: os.fdopen now raises an OSError for invalid file descriptors.

- Issue #4838: When a module is deallocated, free the memory backing the
  optional module state data.

- Issue #4910: Rename nb_long slot to nb_reserved, and change its
  type to (void *).

- Issue #4935: The overflow checking code in the expandtabs() method common
  to str, bytes and bytearray could be optimized away by the compiler, letting
  the interpreter segfault instead of raising an error.

- Issue #3720: Fix a crash when an iterator modifies its class and removes its
  __next__ method.

- Issue #4910: Builtin int() function and PyNumber_Long/PyNumber_Int API
  function no longer attempt to call the __long__ slot to convert an object
  to an integer.  Only the __int__ and __trunc__ slots are examined.

- Issue #4893: Use NT threading on CE.

- Issue #4915: Port sysmodule to Windows CE.

- Issue #4868: utf-8, utf-16 and latin1 decoding are now 2x to 4x faster. The
  common cases are optimized thanks to a dedicated fast path and a moderate
  amount of loop unrolling.

- Issue #4074: Change the criteria for doing a full garbage collection (i.e.
  collecting the oldest generation) so that allocating lots of objects without
  destroying them does not show quadratic performance. Based on a proposal by
  Martin von Löwis at
  http://mail.python.org/pipermail/python-dev/2008-June/080579.html.

- Issue #4604: Some objects of the I/O library could still be used after
  having been closed (for instance, a read() call could return some
  previously buffered data). Patch by Dmitry Vasiliev.

- Issue #4705: Fix the -u ("unbuffered binary stdout and stderr") command-line
  flag to work properly. Furthermore, when specifying -u, the text stdout
  and stderr streams have line-by-line buffering enabled (the default being
  to buffer arbitrary chunks of data).

- The internal table, _PyLong_DigitValue, is now an array of unsigned chars
  instead of ints (reducing its size from 4 to 8 times thereby reducing
  Python's overall memory).

- Issue #1180193: When importing a module from a .pyc (or .pyo) file with
  an existing .py counterpart, override the co_filename attributes of all
  code objects if the original filename is obsolete (which can happen if the
  file has been renamed, moved, or if it is accessed through different paths).
  Patch by Ziga Seilnacht and Jean-Paul Calderone.

- Issue #4580: Fix slicing of memoryviews when the item size is greater than
  one byte. Also fixes the meaning of len() so that it returns the number of
  items, rather than the size in bytes.

- Issue #4075: Use OutputDebugStringW in Py_FatalError.

- Issue #4747: When the terminal does not use utf-8, executing a script with
  non-ascii characters in its name could fail with a "SyntaxError: None" error.

- Issue #4797: IOError.filename was not set when _fileio.FileIO failed to open
  file with `bytes' filename on Windows.

- Issue #3680: Reference cycles created through a dict, set or deque iterator
  did not get collected.

- Issue #4701: PyObject_Hash now implicitly calls PyType_Ready on types
  where the tp_hash and tp_dict slots are both NULL.

- Issue #4759: None is now allowed as the first argument of
  bytearray.translate().  It was always allowed for bytes.translate().

- Added test case to ensure attempts to read from a file opened for writing
  fail.

- Issue #3106: Speedup some comparisons (str/str and int/int).

- Issue #2183: Simplify and optimize bytecode for list, dict and set
  comprehensions. Original patch for list comprehensions by Neal Norwitz.

- Issue #2467: gc.DEBUG_STATS reported invalid elapsed times. Also, always
  print elapsed times, not only when some objects are uncollectable /
  unreachable. Original patch by Neil Schemenauer.

- Issue #3439: Add a bit_length method to int.

- Issue #2173: When getting device encoding, check that return value of
  nl_langinfo is not the empty string.  This was causing silent build
  failures on OS X.

- Issue #4597: Fixed several opcodes that weren't always propagating
  exceptions.

- Issue #4589: Fixed exception handling when the __exit__ function of a
  context manager returns a value that cannot be converted to a bool.

- Issue #4445: Replace "sizeof(PyBytesObject)" with
  "offsetof(PyBytesObject, ob_sval) + 1" when allocating memory for
  bytes instances.  On a typical machine this saves 3 bytes of memory
  (on average) per allocation of a bytes instance.

- Issue #4533: File read operation was dreadfully slow due to a slowly
  growing read buffer. Fixed by using the same growth rate algorithm as
  Python 2.x.

- Issue #4509: Various issues surrounding resize of bytearray objects to
  which there are buffer exports (e.g. memoryview instances).

- Issue #4233: Changed semantic of ``_fileio.FileIO``'s ``close()``
  method on file objects with closefd=False. The file descriptor is still
  kept open but the file object behaves like a closed file. The ``FileIO``
  object also got a new readonly attribute ``closefd``.

- Issue #4569: Interpreter crash when mutating a memoryview with an item size
  larger than 1.

- Issue #4748: Lambda generators no longer return a value.

- The re.sub(), re.subn() and re.split() functions now accept a flags parameter.

- Issue #5108: Handle %s like %S, %R and %A in PyUnicode_FromFormatV(): Call
  PyUnicode_DecodeUTF8() once, remember the result and output it in a second
  step. This avoids problems with counting UTF-8 bytes that ignores the effect
  of using the replace error handler in PyUnicode_DecodeUTF8().

Library
-------

- Issue #6365: Distutils build_ext inplace mode was copying the compiled 
  extension in a subdirectory if the extension name had dots.

- Issue #6164: Added an AIX specific linker argument in Distutils 
  unixcompiler. Original patch by Sridhar Ratnakumar.

- Issue #6286: Now Distutils upload command is based on urllib2 instead of
  httplib, allowing the usage of http_proxy.

- Issue #6287: Added the license field in Distutils documentation.

- Issue #6263: Fixed syntax error in distutils.cygwincompiler.

- Issue #5201: distutils.sysconfig.parse_makefile() now understands `$$`
  in Makefiles. This prevents compile errors when using syntax like:
  `LDFLAGS='-rpath=\$$LIB:/some/other/path'`. Patch by Floris Bruynooghe.

- Issue #6131: test_modulefinder leaked when run after test_distutils.
  Patch by Hirokazu Yamamoto.

- Issue #6048: Now Distutils uses the tarfile module in archive_util.

- Issue #6062: In distutils, fixed the package option of build_ext. Feedback
  and tests on pywin32 by Tim Golden.

- Issue #6053: Fixed distutils tests on win32. patch by Hirokazu Yamamoto.

- Issue #6046: Fixed the library extension when distutils build_ext is used
  inplace. Initial patch by Roumen Petrov.

- Issue #6041: Now distutils `sdist` and `register` commands use `check` as a
  subcommand.

- Issue #6022: a test file was created in the current working directory by
  test_get_outputs in Distutils.

- Issue #5977: distutils build_ext.get_outputs was not taking into account the
  inplace option. Initial patch by kxroberto.

- Issue #5984: distutils.command.build_ext.check_extensions_list checks were broken
  for old-style extensions.

- Issue #5976: Fixed Distutils test_check_environ.

- Issue #5941: Distutils build_clib command was not working anymore because
  of an incomplete costumization of the archiver command. Added ARFLAGS in the
  Makefile besides AR and make Distutils use it. Original patch by David
  Cournapeau.

- Issue #2245: aifc now skips chunk types it doesn't recognize, per spec.

- Issue #5874: distutils.tests.test_config_cmd is not locale-sensitive
  anymore.

- Issue #5810: Fixed Distutils test_build_scripts so it uses
  sysconfig.get_config_vars.

- Issue #4951: Fixed failure in test_httpservers.

- Issue #5795: Fixed test_distutils failure on Debian ppc.

- Issue #5607: fixed Distutils test_get_platform for Mac OS X fat binaries.

- Issue #5741: don't disallow "%%" (which is an escape for "%") when setting
  a value in SafeConfigParser.

- Issue #5732: added a new command in Distutils: check.

- Issue #5731: Distutils bdist_wininst no longer worked on non-Windows
  platforms. Initial patch by Paul Moore.

- Issue #5095: Added bdist_msi to the list of bdist supported formats.
  Initial fix by Steven Bethard.

- Issue #1491431: Fixed distutils.filelist.glob_to_re for edge cases.
  Initial fix by Wayne Davison.

- Issue #5694: removed spurious test output in Distutils (test_clean).

- Issue #1326077: fix the formatting of SyntaxErrors by the traceback module.

- Issue #1665206 (partially): Move imports in cgitb to the top of the module
  instead of performing them in functions. Helps prevent import deadlocking in
  threads.

- Issue #2522: locale.format now checks its first argument to ensure it has
  been passed only one pattern, avoiding mysterious errors where it appeared
  that it was failing to do localization.

- Issue #5583: Added optional Extensions in Distutils. Initial patch by Georg
  Brandl.

- Issue #1222: locale.format() bug when the thousands separator is a space
  character.

- Issue #5472: Fixed distutils.test_util tear down. Original patch by
  Tim Golden.

- collections.deque() objects now have a read-only attribute called maxlen.

- Issue #2638: Show a window constructed with tkSimpleDialog.Dialog only after
  it is has been populated and properly configured in order to prevent
  window flashing.

- Issue #4792: Prevent a segfault in _tkinter by using the
  guaranteed to be safe interp argument given to the PythonCmd in place of
  the Tcl interpreter taken from a PythonCmd_ClientData.

- Issue #5193: Guarantee that tkinter.Text.search returns a string.

- Issue #5394: removed > 2.3 syntax from distutils.msvc9compiler.
  Original patch by Akira Kitada.

- Issue #5334: array.fromfile() failed to insert values when EOFError was raised.

- Issue #5385: Fixed mmap crash after resize failure on windows.

- Issue #5179: Fixed subprocess handle leak on failure on windows.

- PEP 372:  Added collections.OrderedDict().

- The _asdict() for method for namedtuples now returns an OrderedDict().

- configparser now defaults to using an ordered dictionary.

- Issue #5401: Fixed a performance problem in mimetypes when ``from mimetypes
  import guess_extension`` was used.

- Issue #1733986: Fixed mmap crash in accessing elements of second map object
  with same tagname but larger size than first map. (Windows)

- Issue #5386: mmap.write_byte didn't check map size, so it could cause buffer
  overrun.

- Issue #1533164: Installed but not listed *.pyo was breaking Distutils
  bdist_rpm command.

- Issue #5378: added --quiet option to Distutils bdist_rpm command.

- Issue #5052: make Distutils compatible with 2.3 again.

- Issue #5316: Fixed buildbot failures introduced by multiple inheritance
  in Distutils tests.

- Issue #5287: Add exception handling around findCaller() call to help out
  IronPython.

- Issue #5282: Fixed mmap resize on 32bit windows and unix. When offset > 0,
  The file was resized to wrong size.

- Issue #5292: Fixed mmap crash on its boundary access m[len(m)].

- Issue #2279: distutils.sdist.add_defaults now add files
  from the package_data and the data_files metadata.

- Issue #5257: refactored all tests in distutils, so they use
  support.TempdirManager, to avoid writing in the tests directory.

- Issue #4524: distutils build_script command failed with --with-suffix=3.
  Initial patch by Amaury Forgeot d'Arc.

- Issue #2461: added tests for distutils.util

- Issue #4998: The memory saving effect of __slots__ had been lost on Fractions
  which inherited from numbers.py which did not have __slots__ defined.  The
  numbers hierarchy now has its own __slots__ declarations.

- Issue #4631: Fix urlopen() result when an HTTP response uses chunked
  encoding.

- Issue #5203: Fixed ctypes segfaults when passing a unicode string to a
  function without argtypes (only occurs if HAVE_USABLE_WCHAR_T is false).

- Issue #3386: distutils.sysconfig.get_python_lib prefix argument was ignored
  under NT and OS2. Patch by Philip Jenvey.

- Issue #5128: Make compileall properly inspect bytecode to determine if needs
  to be recreated. This avoids a timing hole thanks to the old reliance on the
  ctime of the files involved.

- Issue #5122: Synchronize tk load failure check to prevent a potential
  deadlock.

- Issue #1818: collections.namedtuple() now supports a keyword argument
  'rename' which lets invalid fieldnames be automatically converted to
  positional names in the form, _1, _2, ...

- Issue #4890: Handle empty text search pattern in Tkinter.Text.search.

- Issue #4512 (part 2): Promote ``ZipImporter._get_filename()`` to be a
  public documented method ``ZipImporter.get_filename()``.

- Issue #4195: The ``runpy`` module (and the ``-m`` switch) now support
  the execution of packages by looking for and executing a ``__main__``
  submodule when a package name is supplied. Initial patch by Andi
  Vajda.

- Issue #1731706: Call Tcl_ConditionFinalize for Tcl_Conditions that will
  not be used again (this requires Tcl/Tk 8.3.1), also fix a memory leak in
  Tkapp_Call when calling from a thread different than the one that created
  the Tcl interpreter. Patch by Robert Hancock.

- Issue #4285: Change sys.version_info to be a named tuple. Patch by
  Ross Light.

- Issue #1520877: Now distutils.sysconfig reads $AR from the
  environment/Makefile. Patch by Douglas Greiman.

- Issue #1276768: The verbose option was not used in the code of
  distutils.file_util and distutils.dir_util.

- Issue #5132: Fixed trouble building extensions under Solaris with
  --enabled-shared activated. Initial patch by Dave Peterson.

- Issue #1581476: Always use the Tcl global namespace when calling into Tcl.

- The shelve module now defaults to pickle protocol 3.

- Fix a bug in the trace module where a bytes object from co_lnotab had its
  items being passed through ord().

- Issue #2047: shutil.move() could believe that its destination path was
  inside its source path if it began with the same letters (e.g. "src" vs.
  "src.new").

- Added the ttk module. See issue #2983: Ttk support for Tkinter.

- Removed isSequenceType(), isMappingType, and isNumberType() from the
  operator module; use the abstract base classes instead.  Also removed
  the repeat() function; use mul() instead.

- Issue #5021:  doctest.testfile() did not create __name__ and
  collections.namedtuple() relied on __name__ being defined.

- Backport importlib from Python 3.1. Only the import_module() function has
  been backported to help facilitate transitions from 2.7 to 3.1.

- Issue #1885: distutils. When running sdist with --formats=tar,gztar
  the tar file was overriden by the gztar one.

- Issue #4863: distutils.mwerkscompiler has been removed.

- Added a new itertools functions:  combinations_with_replacement()
  and compress().

- Issue #5032:  added a step argument to itertools.count() and
  allowed non-integer arguments.

- Fix and properly document the multiprocessing module's logging
  support, expose the internal levels and provide proper usage
  examples.

- Issue #1672332: fix unpickling of subnormal floats, which was
  producing a ValueError on some platforms.

- Issue #3881: Help Tcl to load even when started through the
  unreadable local symlink to "Program Files" on Vista.

- Issue #4710: Extract directories properly in the zipfile module;
  allow adding directories to a zipfile.

- Issue #3807: _multiprocessing build fails when configure is passed
  --without-threads argument. When this occurs, _multiprocessing will
  be disabled, and not compiled.

- Issue #5008: When a file is opened in append mode with the new IO library,
  do an explicit seek to the end of file (so that e.g. tell() returns the
  file size rather than 0). This is consistent with the behaviour of the
  traditional 2.x file object.

- Issue #5013: Fixed a bug in FileHandler which occurred when the delay
  parameter was set.

- Issue #4842: Always append a trailing 'L' when pickling longs using
  pickle protocol 0.  When reading, the 'L' is optional.

- Add the importlib package.

- Issue #4301: Patch the logging module to add processName support, remove
  _check_logger_class from multiprocessing.

- Issue #3325: Remove python2.x try: except: imports for old cPickle from
  multiprocessing.

- Issue #4959: inspect.formatargspec now works for keyword only arguments
  without defaults.

- Issue #3321: _multiprocessing.Connection() doesn't check handle; added checks
  for *nix machines for negative handles and large int handles. Without this check
  it is possible to segfault the interpreter.

- Issue #4449: AssertionError in mp_benchmarks.py, caused by an underlying issue
  in sharedctypes.py.

- Issue #1225107: inspect.isclass() returned True for instances with a custom
  __getattr__.

- Issue #3826 and #4791: The socket module now closes the underlying socket
  appropriately when it is being used via socket.makefile() objects
  rather than delaying the close by waiting for garbage collection to do it.

- Issue #1696199:  Add collections.Counter() for rapid and convenient
  counting.

- Issue #3860: GzipFile and BZ2File now support the context manager protocol.

- Issue #4867: Fixed a crash in ctypes when passing a string to a
  function without defining argtypes.

- Issue #4272: Add an optional argument to the GzipFile constructor to override
  the timestamp in the gzip stream. The default value remains the current time.
  The information can be used by e.g. gunzip when decompressing. Patch by
  Jacques Frechet.

- Restore Python 2.3 compatibility for decimal.py.

- Issue #3638: Remove functions from _tkinter module level that depend on
  TkappObject to work with multiple threads.

- Issue #4718: Adapt the wsgiref package so that it actually works with
  Python 3.x, in accordance with the `official amendments of the spec
  <http://www.wsgi.org/wsgi/Amendments_1.0>`_.

- Issue #4796: Added Decimal.from_float() and Context.create_decimal_from_float()
  to the decimal module.

- Fractions.from_float() no longer loses precision for integers too big to
  cast as floats.

- Issue #4812: add missing underscore prefix to some internal-use-only
  constants in the decimal module.  (Dec_0 becomes _Dec_0, etc.)

- Issue #4790: The nsmallest() and nlargest() functions in the heapq module
  did unnecessary work in the common case where no key function was specified.

- Issue #4795: inspect.isgeneratorfunction() returns False instead of None when
  the function is not a generator.

- Issue #4702: Throwing a DistutilsPlatformError instead of IOError in case
  no MSVC compiler is found under Windows. Original patch by Philip Jenvey.

- Issue #4646: distutils was choking on empty options arg in the setup
  function. Original patch by Thomas Heller.

- Issue #3767: Convert Tk object to string in tkColorChooser.

- Issue #3248: Allow placing ScrolledText in a PanedWindow.

- Issue #4444: Allow assertRaises() to be used as a context handler, so that
  the code under test can be written inline if more practical.

- Issue #4739: Add pydoc help topics for symbols, so that e.g. help('@')
  works as expected in the interactive environment.

- Issue #4756: zipfile.is_zipfile() now supports file-like objects. Patch by
  Gabriel Genellina.

- Issue #4574: reading an UTF16-encoded text file crashes if \r on 64-char
  boundary.

- Issue #4223: inspect.getsource() will now correctly display source code
  for packages loaded via zipimport (or any other conformant PEP 302
  loader). Original patch by Alexander Belopolsky.

- Issue #4201: pdb can now access and display source code loaded via
  zipimport (or any other conformant PEP 302 loader). Original patch by
  Alexander Belopolsky.

- Issue #4197: doctests in modules loaded via zipimport (or any other PEP
  302 conformant loader) will now work correctly in most cases (they
  are still subject to the constraints that exist for all code running
  from inside a module loaded via a PEP 302 loader and attempting to
  perform IO operations based on __file__). Original patch by
  Alexander Belopolsky.

- Issues #4082 and #4512: Add runpy support to zipimport in a manner that
  allows backporting to maintenance branches. Original patch by
  Alexander Belopolsky.

- Issue #4163: textwrap module: allow word splitting on a hyphen preceded by
  a non-ASCII letter.

- Issue #4616: TarFile.utime(): Restore directory times on Windows.

- Issue #4021: tokenize.detect_encoding() now raises a SyntaxError when the
  codec cannot be found.  This is for compatibility with the builtin behavior.

- Issue #4084: Fix max, min, max_mag and min_mag Decimal methods to
  give correct results in the case where one argument is a quiet NaN
  and the other is a finite number that requires rounding.

- Issue #4483: _dbm module now builds on systems with gdbm & gdbm_compat
  libs.

- Added the subprocess.check_call_output() convenience function to get output
  from a subprocess on success or raise an exception on error.

- Issue #1055234: cgi.parse_header(): Fixed parsing of header parameters to
  support unusual filenames (such as those containing semi-colons) in
  Content-Disposition headers.

- Issue #4384: Added logging integration with warnings module using
  captureWarnings(). This change includes a NullHandler which does nothing;
  it will be of use to library developers who want to avoid the "No handlers
  could be found for logger XXX" message which can appear if the library user
  doesn't configure logging.

- Issue #3741: DISTUTILS_USE_SDK set causes msvc9compiler.py to raise an
  exception.

- Issue #4529: fix the parser module's validation of try-except-finally
  statements.

- Issue #4458: getopt.gnu_getopt() now recognizes a single "-" as an argument,
  not a malformed option.

- Added the subprocess.check_output() convenience function to get output
  from a subprocess on success or raise an exception on error.

- Issue #4542: On Windows, binascii.crc32 still accepted str as binary input;
  the corresponding tests now pass.

- Issue #4537: webbrowser.UnixBrowser would fail to open the browser because
  it was calling the wrong open() function.

- Issue #1055234: cgi.parse_header(): Fixed parsing of header parameters to
  support unusual filenames (such as those containing semi-colons) in
  Content-Disposition headers.

- Issue #4861: ctypes.util.find_library(): Robustify. Fix library detection on
  biarch systems. Try to rely on ldconfig only, without using objdump and gcc.

- Issue #5104: The socket module now raises OverflowError when 16-bit port and
  protocol numbers are supplied outside the allowed 0-65536 range on bind()
  and getservbyport().

- Windows locale mapping updated to Vista.

Tools/Demos
-----------

- Issue #4704: remove use of cmp() in pybench, bump its version number to 2.1,
  and make it 2.6-compatible.

- Ttk demos added in Demo/tkinter/ttk/

- Issue #4677: add two list comprehension tests to pybench.


Build
-----

- Issue #6094: Build correctly with Subversion 1.7.

- Issue #5847: Remove -n switch on "Edit with IDLE" menu item.

- Issue #5726: Make Modules/ld_so_aix return the actual exit code of the
  linker, rather than always exit successfully. Patch by Floris Bruynooghe.

- Issue #4587: Add configure option --with-dbmliborder=db1:db2:... to specify
  the order that backends for the dbm extension are checked.

- Link the shared python library with $(MODLIBS).

- Issue #5134: Silence compiler warnings when compiling sqlite with VC++.

- Issue #4494: Fix build with Py_NO_ENABLE_SHARED on Windows.

- Issue #4895: Use _strdup on Windows CE.

- Issue #4472: "configure --enable-shared" now works on OSX

- Issues #4728 and #4060: WORDS_BIGEDIAN is now correct in Universal builds.

- Issue #4389: Add icon to the uninstall entry in "add-and-remove-programs".

- Issue #4289: Remove Cancel button from AdvancedDlg.

- Issue #1656675: Register a drop handler for .py* files on Windows.

- Issue #4120: Exclude manifest from extension modules in VS2008.

- Issue #4091: Install pythonxy.dll in system32 again.

- Issue #4018: Disable "for me" installations on Vista.

- Issue #3758: Add ``patchcheck`` build target to .PHONY.

- Issue #4204: Fixed module build errors on FreeBSD 4.


C-API
-----

- Issue #5175: PyLong_AsUnsignedLongLong now raises OverflowError
  for negative arguments.  Previously, it raised TypeError.

- Issue #4720: The format for PyArg_ParseTupleAndKeywords can begin with '|'.

- Issue #3632: from the gdb debugger, the 'pyo' macro can now be called when
  the GIL is released, or owned by another thread.

- Issue #4122: On Windows, fix a compilation error when using the
  Py_UNICODE_ISSPACE macro in an extension module.


Extension Modules
-----------------

- Issue #3745: Fix hashlib to always reject unicode and non buffer-api
  supporting objects as input no matter how it was compiled (built in
  implementations or external openssl library).

- Issue #4397: Fix occasional test_socket failure on OS X.

- Issue #4279: Fix build of parsermodule under Cygwin.

- Issue #4751: hashlib now releases the GIL when hashing large buffers
  (with a hardwired threshold of 2048 bytes), allowing better parallelization
  on multi-CPU systems. Contributed by Lukas Lueg (ebfe) and Victor Stinner.

- Issue #4051: Prevent conflict of UNICODE macros in cPickle.

- Issue #4738: Each zlib object now has a separate lock, allowing to compress
  or decompress several streams at once on multi-CPU systems. Also, the GIL
  is now released when computing the CRC of a large buffer. Patch by ebfe.

- Issue #4228: Pack negative values the same way as 2.4 in struct's L format.

- Issue #1040026: Fix os.times result on systems where HZ is incorrect.

- Issues #3167, #3682: Fix test_math failures for log, log10 on Solaris,
  OpenBSD.

- Issue #4583: array.array would not always prohibit resizing when a buffer
  has been exported, resulting in an interpreter crash when accessing the
  buffer.


- Issue #5228: Make functools.partial objects can now be pickled.

Tests
-----

- Issue #6152: New option '-j'/'--multiprocess' for regrtest allows running
  regression tests in parallel, shortening the total runtime.

- Issue #5450: Moved tests involving loading tk from Lib/test/test_tcl to
  Lib/tkinter/test/test_tkinter/test_loadtk. With this, these tests demonstrate
  the same behaviour as test_ttkguionly (and now also test_tk) which is to
  skip the tests if DISPLAY is defined but can't be used.

- regrtest no longer treats ImportError as equivalent to SkipTest.  Imports
  that should cause a test to be skipped are now done using import_module
  from test support, which does the conversion.

- Issue #5083: New 'gui' resource for regrtest.


Docs
----


**(For information about older versions, consult the HISTORY file.)**