Also monkey-patch threading._Event on Python 2. Fixes #1136

CHANGES.rst

@@ -10,6 +10,10 @@
 - Use strongly typed watcher callbacks in the libuv CFFI extensions.
   This prevents dozens of compiler warnings.
 
+- On Python 2, when monkey-patching `threading.Event`, also
+  monkey-patch the underlying class, ``threading._Event``. Some code
+  may be type-checking for that. See :issue:`1136`.
+
 
 1.3a2 (2018-03-06)
 ==================

src/gevent/monkey.py

@@ -405,6 +405,11 @@ def patch_thread(threading=True, _threading_local=True, Event=True, logging=True
         if Event:
             from gevent.event import Event
             patch_item(threading_mod, 'Event', Event)
+            # Python 2 had `Event` as a function returning
+            # the private class `_Event`. Some code may be relying
+            # on that.
+            if hasattr(threading_mod, '_Event'):
+                patch_item(threading_mod, '_Event', Event)
 
         if existing_locks:
             _patch_existing_locks(threading_mod)

src/greentest/test__monkey.py

@@ -26,12 +26,15 @@ class TestMonkey(unittest.TestCase):
         self.assertIs(thread.start_new_thread, gthread.start_new_thread)
         self.assertIs(threading._start_new_thread, gthread.start_new_thread)
 
+        # Event patched by default
+        self.assertTrue(monkey.is_object_patched('threading', 'Event'))
+
         if sys.version_info[0] == 2:
             from gevent import threading as gthreading
+            from gevent.event import Event as GEvent
             self.assertIs(threading._sleep, gthreading._sleep)
-
-        # Event patched by default
-        self.assertTrue(monkey.is_object_patched('threading', 'Event'))
+            self.assertTrue(monkey.is_object_patched('threading', '_Event'))
+            self.assertIs(threading._Event, GEvent)
 
     def test_socket(self):
         import socket