Set the __test__ attribute on gen_test to False.

bdarnell · bdarnell · commit fc9670029899 · 2013-04-02T00:11:10.000-04:00
Without this, if a nose-using project imported gen_test nose would try
to run it as a test.
diff --git a/tornado/testing.py b/tornado/testing.py
@@ -377,6 +377,11 @@ def wrapper(self):
     return wrapper
 
 
+# Without this attribute, nosetests will try to run gen_test as a test
+# anywhere it is imported.
+gen_test.__test__ = False
+
+
 class LogTrapTestCase(unittest.TestCase):
     """A test case that captures and discards all logging output
     if the test passes.
