Add missing import for unittest.
Two changes went in at once: One that removed all usages of the unittest
module, and one that added a new usage. Since we don't run Chromite unit
tests on the CQ currently, both went in and we have broken unit tests.
TEST=Run cbuildbot_stages_unittest.py and verify it works now.
Tested-by: David James <email@example.com>
Reviewed-by: Matt Tennant <firstname.lastname@example.org>
Commit-Queue: David James <email@example.com>
1 file changed