disable deprecation warnings in prod (bug 654562)

manage.py

@@ -2,6 +2,7 @@
 import os
 import site
 import sys
+import warnings
 
 
 ROOT = os.path.dirname(os.path.abspath(__file__))
@@ -45,6 +46,9 @@ except ImportError:
             " Please come back and try again later.")
         raise
 
+if not settings.DEBUG:
+    warnings.simplefilter('ignore')
+
 # The first thing execute_manager does is call `setup_environ`.  Logging config
 # needs to access settings, so we'll setup the environ early.
 setup_environ(settings)