* Add a new option taking a filename to get a list of test names to
filter tests.
* support.match_tests becomes a list.
* Modify run_unittest() to accept to match the whole test identifier,
not just a part of a test identifier.
For example, the following command only runs test_default_timeout()
of the BarrierTests class of test_threading:
$ ./python -m test -v test_threading -m test.test_threading.BarrierTests.test_default_timeout
Remove also some empty lines from test_regrtest.py to make flake8
tool happy.
