mailpipe: fix InvalidHandlerMessage error message construction.

`target` is an explicit argument, not in `**kwargs`.

I also removed the InvalidHandlerMessage error logging, because we're
raising an exception.  The calling function can log the exception if
it catches it.  If it doesn't, the user will see the message in the
traceback.

diff --git a/pygrader/mailpipe.py b/pygrader/mailpipe.py
index 609ca94aa4fa0bbf80de256c9ca4ca8883758354..92215c6abbf86c1077ffb3c6eae7c0d7f30bbf89 100644 (file)
--- a/pygrader/mailpipe.py
+++ b/pygrader/mailpipe.py
@@ -80,8 +80,7 @@ class SubjectlessMessage (_InvalidSubjectMessage):
 class InvalidHandlerMessage (_InvalidSubjectMessage):
     def __init__(self, target=None, handlers=None, **kwargs):
         if 'error' not in kwargs:
-            kwargs['error'] = 'no handler for {!r}'.format(
-                kwargs.get('target', None))
+            kwargs['error'] = 'no handler for {!r}'.format(target)
         super(InvalidHandlerMessage, self).__init__(**kwargs)
         self.target = target
         self.handlers = handlers
@@ -755,10 +754,9 @@ def _get_message_target(subject):
 def _get_handler(handlers, target):
     try:
         handler = handlers[target]
-    except KeyError:
-        response_subject = 'no handler for {}'.format(target)
-        _LOG.warning(_color_string(string=response_subject))
-        raise InvalidHandlerMessage(target=target, handlers=handlers)
+    except KeyError as error:
+        raise InvalidHandlerMessage(
+            target=target, handlers=handlers) from error
     return handler
 
 def _get_verified_message(message, pgp_key):