vndk-def: Fix deprecated warning in unittest

This commit adds a TestCase compatibility layer to support `assertRegex`
and `assertNotRegex` in both Python 2.7 and 3.5.  This removes a
deprecated warning while running test cases with Python 3.5.

Test: ./tests/run.sh
Change-Id: I9856b08f18ae92d110f37f75d444f09692f08acf
3 files changed