Switch all urllib/urlparse usage to six.moves.urllib.

This provides Python 2+3 compatibility for our use of urllib.

Also add a test to avoid future regressions.

integrations/asana/zulip_asana_mirror

@@ -37,7 +37,7 @@ import json
 import logging
 import os
 import time
-import urllib2
+from six.moves import urllib
 
 import sys
 
@@ -74,8 +74,8 @@ def fetch_from_asana(path):
     headers = {"Authorization": "Basic %s" % auth}
 
     url = "https://app.asana.com/api/1.0" + path
-    request = urllib2.Request(url, None, headers)
-    result = urllib2.urlopen(request)
+    request = urllib.request.Request(url, None, headers)
+    result = urllib.request.urlopen(request)
 
     return json.load(result)