bpo-30540: regrtest: add --matchfile option (#1909)

* 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.

1 files changed, 8 insertions, 2 deletions

diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index d8d599b..0a3d4d9 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -1922,9 +1922,15 @@ def run_unittest(*classes):
     def case_pred(test):
         if match_tests is None:
             return True
-        for name in test.id().split("."):
-            if fnmatch.fnmatchcase(name, match_tests):
+        test_id = test.id()
+
+        for match_test in match_tests:
+            if fnmatch.fnmatchcase(test_id, match_test):
                 return True
+
+            for name in test_id.split("."):
+                if fnmatch.fnmatchcase(name, match_test):
+                    return True
         return False
     _filter_suite(suite, case_pred)
     _run_suite(suite)