Add unittest2 testing to trial environment

Just noticed that `test_usefixtures_marker_on_unittest` is parametrized
for unittest2, but no environment ever installed that library.

1 files changed, 1 insertions, 0 deletions

diff --git a/tox.ini b/tox.ini
index 59879ead3..87a56f842 100644
--- a/tox.ini
+++ b/tox.ini
@@ -83,6 +83,7 @@ commands =
 deps =
     {[testenv]deps}
     twisted
+    unittest2
 commands =
     {env:_PYTEST_TOX_COVERAGE_RUN:} pytest {posargs:testing/test_unittest.py}