Add queries_captured() context manager for tests.

(imported from commit 14a9529aef057e79bc12c979d88b595828a8b3a3)

zerver/tests.py

@@ -28,6 +28,7 @@ from zerver.forms import not_mit_mailing_list
 
 import base64
 from django.conf import settings
+from django.db import connection
 import os
 import random
 import re
@@ -50,6 +51,19 @@ def tornado_redirected_to_list(lst):
     yield
     tornado_callbacks.process_event = real_tornado_callbacks_process_event
 
+@contextmanager
+def queries_captured():
+    '''
+    Allow a user to capture just the queries executed during
+    the with statement.
+    '''
+    old_settings = settings.DEBUG
+    settings.DEBUG = True
+    connection.queries = []
+    yield connection.queries
+    settings.DEBUG = old_settings
+
+
 def bail(msg):
     print '\nERROR: %s\n' % (msg,)
     sys.exit(1)