This commit fixes a couple of bugs in the blacklist file regex
generator. The first where a comment line was accidently made
mandatory. If a comment wasn't specified an IndexError would be
raised. The second was related to the variable naming in the
function's blacklist file if branch. Variable reuse there was causing
the last blacklist regex to take precendence over a regex passed
in and would be used instead.
Change-Id: Ib80a0c1781db7c8c9e4449b4773258fe3348411a
Closes-Bug: #1488700
d533445b26