Issue 7815. __unittest in module globals trims frames from reported stacktraces in unittest.
diff --git a/Lib/unittest/suite.py b/Lib/unittest/suite.py
index cccc7ef..0dd2dc5 100644
--- a/Lib/unittest/suite.py
+++ b/Lib/unittest/suite.py
@@ -5,6 +5,8 @@
 from . import case
 from . import util
 
+__unittest = True
+
 
 class BaseTestSuite(object):
     """A simple test suite that doesn't provide class or module shared fixtures.