Add ping method to auth engines to determine if they are reachable

data/users/database.py

@@ -5,6 +5,10 @@ class DatabaseUsers(object):
   def federated_service(self):
     return None
 
+  def ping(self):
+    """ Always assumed to be working. If the DB is broken, other checks will handle it. """
+    return (True, None)
+
   def verify_credentials(self, username_or_email, password):
     """ Simply delegate to the model implementation. """
     result = model.user.verify_user(username_or_email, password)