Fix pyflakes warning

test_socket_manager.py:11: '__pypy__' imported but unused

supervisor/tests/test_socket_manager.py

@@ -9,9 +9,8 @@ import tempfile
 
 try:
     import __pypy__
-    PYPY = True
 except ImportError:
-    PYPY = False
+    __pypy__ = None
 
 from supervisor.tests.base import DummySocketConfig
 from supervisor.tests.base import DummyLogger
@@ -232,7 +231,7 @@ class SocketManagerTest(unittest.TestCase):
             self.assertEqual(e.args[0], 'Socket has not been prepared')
 
 def gc_collect():
-    if PYPY:
+    if __pypy__ is not None:
         gc.collect()
         gc.collect()
         gc.collect()