Change socket.error to inherit from IOError rather than being a stand

alone class.  This addresses the primary concern in

 http://bugs.python.org/issue1706815

python-dev discussion here:

 http://mail.python.org/pipermail/python-dev/2007-July/073749.html

I chose IOError rather than EnvironmentError as the base class since
socket objects are often used as transparent duck typed file objects
in code already prepared to deal with IOError exceptions.

also a minor fix:

 urllib2 - fix a couple places where IOError was raised rather than URLError.
           for better or worse, URLError already inherits from IOError so
           this won't break any existing code.

 test_urllib2net - replace bad ftp urls.

Doc/library/exceptions.rst

@@ -170,6 +170,9 @@ The following exceptions are the exceptions that are actually raised.
    This class is derived from :exc:`EnvironmentError`.  See the discussion above
    for more information on exception instance attributes.
 
+   .. versionchanged:: 2.6
+      Changed :exc:`socket.error` to use this as a base class.
+
 
 .. exception:: ImportError
 

Doc/library/socket.rst

@@ -86,6 +86,9 @@ The module :mod:`socket` exports the following constants and functions:
    accompanying :exc:`os.error`. See the module :mod:`errno`, which contains names
    for the error codes defined by the underlying operating system.
 
+   .. versionchanged:: 2.6
+      :exc:`socket.error` is now a child class of :exc:`IOError`.
+
 
 .. exception:: herror
 

Doc/whatsnew/2.6.rst

@@ -282,7 +282,8 @@ Porting to Python 2.6
 This section lists previously described changes that may require changes to your
 code:
 
-* Everything is all in the details!
+* The :mod:`socket` module exception :exc:`socket.error` now inherits from 
+  :exc:`IOError`.
 
 .. % ======================================================================
 

Lib/test/test_urllib2net.py

@@ -166,8 +166,9 @@ class OtherNetworkTests(unittest.TestCase):
 
     def test_ftp(self):
         urls = [
-            'ftp://www.python.org/pub/python/misc/sousa.au',
-            'ftp://www.python.org/pub/tmp/blat',
+            'ftp://ftp.kernel.org/pub/linux/kernel/README',
+            'ftp://ftp.kernel.org/pub/linux/kernel/non-existant-file',
+            #'ftp://ftp.kernel.org/pub/leenox/kernel/test',
             'ftp://gatekeeper.research.compaq.com/pub/DEC/SRC'
                 '/research-reports/00README-Legal-Rules-Regs',
             ]
@@ -181,10 +182,7 @@ class OtherNetworkTests(unittest.TestCase):
             f.close()
             urls = [
                 'file:'+sanepathname2url(os.path.abspath(TESTFN)),
-
-                # XXX bug, should raise URLError
-                #('file://nonsensename/etc/passwd', None, urllib2.URLError)
-                ('file://nonsensename/etc/passwd', None, (EnvironmentError, socket.error))
+                ('file:///nonsensename/etc/passwd', None, urllib2.URLError),
                 ]
             self._test_urls(urls, self._extra_handlers())
         finally:
@@ -244,11 +242,11 @@ class OtherNetworkTests(unittest.TestCase):
             debug(url)
             try:
                 f = urllib2.urlopen(url, req)
-            except (IOError, socket.error, OSError), err:
+            except EnvironmentError, err:
                 debug(err)
                 if expected_err:
-                    msg = ("Didn't get expected error(s) %s for %s %s, got %s" %
-                           (expected_err, url, req, err))
+                    msg = ("Didn't get expected error(s) %s for %s %s, got %s: %s" %
+                           (expected_err, url, req, type(err), err))
                     self.assert_(isinstance(err, expected_err), msg)
             else:
                 with test_support.transient_internet():

Lib/urllib2.py

@@ -1246,7 +1246,7 @@ class FTPHandler(BaseHandler):
         import mimetypes
         host = req.get_host()
         if not host:
-            raise IOError, ('ftp error', 'no host given')
+            raise URLError, ('ftp error', 'no host given')
         host, port = splitport(host)
         if port is None:
             port = ftplib.FTP_PORT
@@ -1292,7 +1292,7 @@ class FTPHandler(BaseHandler):
             headers = mimetools.Message(sf)
             return addinfourl(fp, headers, req.get_full_url())
         except ftplib.all_errors, msg:
-            raise IOError, ('ftp error', msg), sys.exc_info()[2]
+            raise URLError, ('ftp error', msg), sys.exc_info()[2]
 
     def connect_ftp(self, user, passwd, host, port, dirs, timeout):
         fw = ftpwrapper(user, passwd, host, port, dirs, timeout)

Modules/socketmodule.c

@@ -4280,7 +4280,8 @@ init_socket(void)
 	if (m == NULL)
 		return;
 
-	socket_error = PyErr_NewException("socket.error", NULL, NULL);
+	socket_error = PyErr_NewException("socket.error",
+					  PyExc_IOError, NULL);
 	if (socket_error == NULL)
 		return;
         PySocketModuleAPI.error = socket_error;