TestUncollectedWarnings failures under pypy

[Wouter van Heyst]

The following tests from bzrlib.tests.test_selftest.TestUncollectedWarnings fail:

    test_additonal_decorator
    test_exclude_pattern
    test_pattern
    test_random_seed
    test_starting_with_and_exclude
    test_testsuite

The odd one out is test_matching_tests_first, which completes fine. The testoutput is a bit hard to read and pdb doesn't get me much further.

[Wouter van Heyst (larstiq)]

Reading some more of the code I decided to run `pypy ./bzr selftest -Euncollected_cases -s bzrlib.tests.blackbox.test_branch` as an example. None of the tests get collected, so it seems it is a more general problem with the feature not working well with pypy.

Adding -f (as suggested by test_matching_tests_first not failing) did not seem to help.

[Martin Pool (mbp)]

This seems to be testing gc-dependent behaviour of tests warning if
they're not collected. The behaviour is obviously going to be
different on pypy (and other Python implementations), so I would be ok
with just making it skip if it's not cpython. gz might feel
differently.

If we suspect there is test infrastructure accumulating in memory when
running under pypy we might need to work out some other way to test
for that.

[Wouter van Heyst (larstiq)]

Discussion on irc with gz confirms that point of view. I'll see if there is a nice way to detect a refcounting gc and if not just skip under pypy.