diff -ru python-dateutil-2.7.2.orig/dateutil/tz/tz.py python-dateutil-2.7.2/dateutil/tz/tz.py
--- python-dateutil-2.7.2.orig/dateutil/tz/tz.py	2018-04-24 18:33:38.436301176 -0400
+++ python-dateutil-2.7.2/dateutil/tz/tz.py	2018-04-24 18:34:39.653365591 -0400
@@ -16,7 +16,6 @@

 import six
 from six import string_types
-from six.moves import _thread
 from ._common import tzname_in_python2, _tzinfo
 from ._common import tzrangebase, enfold
 from ._common import _validate_fromutc_inputs
@@ -33,6 +32,14 @@
 EPOCHORDINAL = EPOCH.toordinal()


+class _dummy_lock:
+    def __enter__(self, *args, **kwargs):
+        pass
+
+    def __exit__(self, *args, **kwargs):
+        pass
+
+
 @six.add_metaclass(_TzSingleton)
 class tzutc(datetime.tzinfo):
     """
@@ -1104,7 +1111,7 @@
         self._comps = comps
         self._cachedate = []
         self._cachecomp = []
-        self._cache_lock = _thread.allocate_lock()
+        self._cache_lock = _dummy_lock()

     def _find_comp(self, dt):
         if len(self._comps) == 1:
@@ -1407,7 +1414,7 @@
         def __init__(self):

             self.__instances = {}
-            self._cache_lock = _thread.allocate_lock()
+            self._cache_lock = _dummy_lock()

         def __call__(self, name=None):
             with self._cache_lock: