Syntax fix for python2

Author: ceball

examples/apps/django2/manage.py

@@ -11,5 +11,5 @@
             "Couldn't import Django. Are you sure it's installed and "
             "available on your PYTHONPATH environment variable? Did you "
             "forget to activate a virtual environment?"
-        ) from exc
+        )
     execute_from_command_line(sys.argv)