Fix all W0602, global used but no assignment done.

common/djangoapps/student/management/commands/massemailtxt.py

@@ -37,7 +37,6 @@ rate -- messages per second
         self.log_file.write(datetime.datetime.utcnow().isoformat() + ' -- ' + text + '\n')
 
     def handle(self, *args, **options):
-        global log_file
         (user_file, message_base, logfilename, ratestr) = args
 
         users = [u.strip() for u in open(user_file).readlines()]

common/lib/xmodule/xmodule/contentstore/django.py

@@ -18,8 +18,6 @@ def load_function(path):
 
 
 def contentstore(name='default'):
-    global _CONTENTSTORE
-
     if name not in _CONTENTSTORE:
         class_ = load_function(settings.CONTENTSTORE['ENGINE'])
         options = {}

common/lib/xmodule/xmodule/modulestore/django.py

@@ -26,8 +26,6 @@ def load_function(path):
 
 
 def modulestore(name='default'):
-    global _MODULESTORES
-
     if name not in _MODULESTORES:
         class_ = load_function(settings.MODULESTORE[name]['ENGINE'])