Changelog:
==========
-Make MetadataPathFinder.find_distributions a classmethod for consistency
with CPython.
-Allow MetadataPathFinder.invalidate_caches to be called as a classmethod.
(From OE-Core rev: 11b074f79bc30115c8a1cfc0119acb3f8f6ea609)
Signed-off-by: Wang Mingyu <wangmy@fujitsu.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
