Fixed #21794 -- Removed deprecation warning for abstract models outside an app.

                msg = (

                    "Model class %s.%s doesn't declare an explicit app_label "

                    "and either isn't in an application in INSTALLED_APPS or "

                    "else was imported before its application was loaded. " %

                    "else was imported before its application was loaded. "

                    "This will no longer be supported in Django 1.9." %

                    (module, name))

                if abstract:

                    msg += "Its app_label will be set to None in Django 1.9."

                else:

                    msg += "This will no longer be supported in Django 1.9."

                if not abstract:

                    warnings.warn(msg, RemovedInDjango19Warning, stacklevel=2)

                model_module = sys.modules[new_class.__module__]