Replace filter(lambda with list comprehension.

filter() returns an iterable on Python 3, not a list

master/buildbot/test/unit/test_changes_gitpoller.py

@@ -152,7 +152,7 @@ def test_get_commit_files_with_space_in_changed_files(self):
             ['log', '--name-only', '--no-walk',
                 '--format=%n', self.dummyRevStr, '--'],
             filesStr,
-            filter(lambda x: x.strip(), filesStr.splitlines(), ),
+            [l for l in filesStr.splitlines() if l.strip()],
             emptyRaisesException=False,
         )