environment_tests.py: Adds test for regex bug

There was a bug in the environment where it returned regex instead of a
string when iterated over. Since the purpose of iterating over
environment was to get values to record in json (and json cannot
serialize regex), this was bad. This adds a test the looks for the regex
members (filter, and exclude_filter) and tests that they have returned a
StringTypes value (a str or unicode instance)

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>