authn: Log a warning message if fallback authentication plugin is enabled in ini file.

rhodecode/authentication/registry.py

@@ -76,6 +76,10 b' class AuthenticationPluginRegistry(objec'
                 plugins.append(plugin)
 
         # Add the fallback plugin from ini file.
+        if self._fallback_plugin:
+            log.warn(
+                'Using fallback authentication plugin from INI file: "%s"',
+                plugin.get_id())
         plugin = self.get_plugin(self._fallback_plugin)
         if plugin is not None and plugin not in plugins:
             plugins.append(plugin)