patcher: [py27] recursion error in pytest/python2.7 installing regist…

…er_at_fork

#660
getsentry/sentry-python#880

Could not reproduce problem without pytest, so normal production code was probably safe.

eventlet/patcher.py

@@ -1,5 +1,7 @@
 import imp
+import os
 import sys
+#_os = original('os')
 
 import eventlet
 import six
@@ -229,7 +231,6 @@ def monkey_patch(**on):
 
     It's safe to call monkey_patch multiple times.
     """
-
     # Workaround for import cycle observed as following in monotonic
     # RuntimeError: no suitable implementation for this system
     # see https://github.com/eventlet/eventlet/issues/401#issuecomment-325015989
@@ -298,6 +299,7 @@ def monkey_patch(**on):
             # tell us whether or not we succeeded
             pass
 
+    _threading = original('threading')
     imp.acquire_lock()
     try:
         for name, mod in modules_to_patch:
@@ -313,10 +315,9 @@ def monkey_patch(**on):
                 if hasattr(orig_mod, attr_name):
                     delattr(orig_mod, attr_name)
 
-            _os = original('os')
-            if name == 'threading' and hasattr(_os, 'register_at_fork'):
+            if name == 'threading' and hasattr(os, 'register_at_fork'):
                 def fix_threading_active(
-                    _global_dict=original('threading').current_thread.__globals__,
+                    _global_dict=_threading.current_thread.__globals__,
                     _patched=orig_mod
                 ):
                     _prefork_active = [None]
@@ -328,7 +329,7 @@ def before_fork():
                     def after_fork():
                         _global_dict['_active'] = _prefork_active[0]
 
-                    _os.register_at_fork(
+                    os.register_at_fork(
                         before=before_fork,
                         after_in_parent=after_fork)
                 fix_threading_active()