Incoming Unicode regular expressions allow brackets inside brackets, therefore POSIX semantics no longer apply. Python warns about possible future breakage, so add backslash escape to square bracket opening inside the character class.
This test suite has been in use for a long time now, in place of the obsolete and unmanageable testparser.py and testfuncs.py. It verifies the complete optimizer output to stdout and stderr, to ensure that the output matches the expectations.
See unit_tests/README.txt for more info.
