homepage

See on Travis CI: https://travis-ci.org/python/cpython/jobs/223771666
Warning -- sys.path was modified by test_site
 Before: (47345855849656, ['', '/usr/local/lib/python37.zip', '/home/travis/build/python/cpython/Lib', '/home/travis/build/python/cpython/build/lib.linux-x86_64-3.7-pydebug'], ['', '/usr/local/lib/python37.zip', '/home/travis/build/python/cpython/Lib', '/home/travis/build/python/cpython/build/lib.linux-x86_64-3.7-pydebug'])
 After: (47345855849656, ['', '/usr/local/lib/python37.zip', '/home/travis/build/python/cpython/Lib', '/home/travis/build/python/cpython/build/lib.linux-x86_64-3.7-pydebug'], ['', '/usr/local/lib/python37.zip', '/home/travis/build/python/cpython/Lib', '/home/travis/build/python/cpython/build/lib.linux-x86_64-3.7-pydebug', '/home/travis/.local/lib/python3.7/site-packages'])

Ah, I reproduced the bug:
$ rmdir ~/.local/lib/python3.7/site-packages; ./python -m test test_site 
Run tests sequentially
0:00:00 [1/1] test_site
Warning -- sys.path was modified by test_site
 Before: (140302199734024, ['', '/home/haypo/prog/GIT/perf', '/usr/local/lib/python37.zip', '/home/haypo/prog/python/master/Lib', '/home/haypo/prog/python/master/build/lib.linux-x86_64-3.7'], ['', '/home/haypo/prog/GIT/perf', '/usr/local/lib/python37.zip', '/home/haypo/prog/python/master/Lib', '/home/haypo/prog/python/master/build/lib.linux-x86_64-3.7'])
 After: (140302199734024, ['', '/home/haypo/prog/GIT/perf', '/usr/local/lib/python37.zip', '/home/haypo/prog/python/master/Lib', '/home/haypo/prog/python/master/build/lib.linux-x86_64-3.7'], ['', '/home/haypo/prog/GIT/perf', '/usr/local/lib/python37.zip', '/home/haypo/prog/python/master/Lib', '/home/haypo/prog/python/master/build/lib.linux-x86_64-3.7', '/home/haypo/.local/lib/python3.7/site-packages']) 
test_site failed (env changed)
1 test altered the execution environment:
 test_site
Total duration: 229 ms
Tests result: SUCCESS

I'm wondering if the user site directory should be removed in tearDownModule().

New changeset b85c136903c6d2368162f7c4a58f258c9c69ead0 by Victor Stinner in branch 'master':
bpo-30108: Restore sys.path in test_site (#1197)
https://github.com/python/cpython/commit/b85c136903c6d2368162f7c4a58f258c9c69ead0

Serhiy Storchaka added the comment:
> I'm wondering if the user site directory should be removed in tearDownModule().
Writing into $HOME/.local is just completely wrong :-) The test suite
must not modify the "system".
On a buildbot, $HOME is the root directory / and so the test is
skipped since the buildbot user is not allowed to create /.local.
If you want to enhance the code: setUpModule() should mock $HOME to
use a temporary directory.

The initial issue (test_site modifies sys.path) has been fixed. I don't think that it's worth it to backport the change, it's just a warning in tests.
@Serhiy: Feel free to open a new issue if you want to enhance test_site ;-)

New changeset 33a5d40de997fff5b60157c546a3bf711e083bcc by Victor Stinner in branch '3.6':
bpo-30108: Restore sys.path in test_site (#1197) (#1378)
https://github.com/python/cpython/commit/33a5d40de997fff5b60157c546a3bf711e083bcc

New changeset 092f4602c329e23b863692249cc630a3eba5b6b5 by Victor Stinner in branch '3.5':
bpo-30108: Restore sys.path in test_site (#1197) (#1379)
https://github.com/python/cpython/commit/092f4602c329e23b863692249cc630a3eba5b6b5

New changeset 78064387e5815633168a80dcdc1bd9aec4eff46a by Victor Stinner in branch '2.7':
bpo-30108: Restore sys.path in test_site (#1197) (#1459)
https://github.com/python/cpython/commit/78064387e5815633168a80dcdc1bd9aec4eff46a

New changeset e81e355a8e43956802211115e3f99859a1a29ecb by Victor Stinner in branch '2.7':
bpo-30108: Fix test_site setUpModule() (#1460)
https://github.com/python/cpython/commit/e81e355a8e43956802211115e3f99859a1a29ecb