Issue 7815. __unittest in module globals trims frames from reported stacktraces in unittest.
diff --git a/Lib/unittest/main.py b/Lib/unittest/main.py
index bd758e0..3f0f43d 100644
--- a/Lib/unittest/main.py
+++ b/Lib/unittest/main.py
@@ -6,6 +6,8 @@
 
 from . import loader, runner
 
+__unittest = True
+
 
 USAGE_AS_MAIN = """\
 Usage: %(progName)s [options] [tests]