unittest2 was needed for Python version <= 2.6, so it hasn't been needed
for quite some time. See unittest2 note one:
https://docs.python.org/2.7/library/unittest.html
This drops unittest2 in favor of the standard unittest module.
Change-Id: I2e787cfbf1709b7f9c889230a10c03689e032957
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>