Re-word error message.

Co-authored-by: Caner Derici <[email protected]>

juju/client/jujudata.py

@@ -82,7 +82,7 @@ def current_controller(self):
         try:
             return self._load_yaml('controllers.yaml', 'current-controller')
         except FileNotFoundError:
-            raise JujuControllerNotFoundError('No controllers.yaml file found. Did you forget to bootstrap Juju?')
+            raise JujuControllerNotFoundError('No controllers.yaml file found. python-libjuju requires a bootstrapped Juju controller.')
 
     def current_model(self, controller_name=None, model_only=False):
         '''Return the current model, qualified by its controller name.