test.test_support.catch_warning is more full-featured and provides the same
functionality.
Since guard_warnings_filter was added in 2.6 there is no
backwards-compatibility issues.
The next step of PEP 352 (for 2.6) causes raising a string exception to trigger
a TypeError. Trying to catch a string exception raises a DeprecationWarning.
References to string exceptions has been removed from the docs since they are
now just an error.
added message attribute compared to the previous version of Exception. It is
also a new-style class, making all exceptions now new-style. KeyboardInterrupt
and SystemExit inherit from BaseException directly. String exceptions now
raise DeprecationWarning.
Applies patch 1104669, and closes bugs 1012952 and 518846.