Fully reverting the relocation also required reverting r66197 (a belated
checkin of test_py3kwarn for the r66135 changes).

There was also a change to test_warnings that had to be reverted (it
appeared to have been mistakenly checked in as part of the checkin that
added the bsddb Py3k warnings).

Running tests now for the full reversion patch. The major objection to
that approach (aside from the issue with external testing of warnings)
is the problem that actually lead to catch_warnings() being relocated in
the first place: suppressing spurious Py3k warnings in modules like cgi.py.

So as much as I was pushing that option earlier, it looks like it isn't
going to be viable.

It's past 1 am here, so I'll be working on the other (cleaner) patch
tomorrow evening.

The intended end result of that other patch:

A warnings.catch_warnings() implementation with the current interface
(i.e. return a list on entry if record=True, None otherwise) that is
intended either to suppress warnings, or to serve as a building block
for better warning testing tools. The patch will also fix the
re-entrancy problem by adding explicit self._entered state guards.

A test_support.catch_warning() implementation which is tailored towards
the needs of the Python regression test suite (probably the
list-with-attributes interface provided by the previous incarnation of
warnings.catch_warning, but with __getattr__ adjusted to return None
when there is no warning caught).