Add the capability to the --no-discover option to convert file
names into regular sexpressions. Also add the --path option that
converts a file or directory to a regular expression. Create a
mutually exclusive argparse group for --regex, --path, and
--no-discover.
This change will allow the user to specify a file name instead of a
regular expression to match a particular set of tests e.g:
tox -e py27 -- --path os_testr/tests/test_os_testr.py
Will run os_testr.tests.test_os_testr but you can use tab complete
to generate the name.
Change-Id: Ibfca2bc023aed44b1b87a0444559ab2a00303a70
aee3402c68