Don't prefix UserVisibleError value in replies

Adding "Command ___ encountered an error" is more likely to confuse than
help when the plugin has deliberately handled the error.

omnipresence/connection.py

@@ -570,9 +570,7 @@ def reply_from_error(self, failure, request):
         message = 'Command \x02{}\x02 encountered an error'.format(
             request.subaction)
         if failure.check(UserVisibleError):
-            self.reply(
-                '{}: {}.'.format(message, failure.getErrorMessage()),
-                error_request)
+            self.reply(failure.getErrorMessage(), error_request)
             return
         log.err(failure, 'Error during command callback: %s %s' %
                 (request.subaction, request.content))

omnipresence/test/test_command.py

@@ -50,7 +50,7 @@ class BasicCommand(EventPlugin):
     def on_command(self, msg):
         args = msg.content.split()
         exc_class = UserVisibleError if 'visible' in args else Exception
-        exc = exc_class('lorem ipsum')
+        exc = exc_class('Lorem ipsum.')
         if 'defer' in args:
             if 'failure' in args:
                 return fail(exc)
@@ -92,8 +92,7 @@ def assert_visible_error(self, deferred_result=None):
         self.assertEqual(self.watcher.last_seen.action, 'privmsg')
         self.assertEqual(self.watcher.last_seen.venue, '#foo')
         self.assertEqual(self.watcher.last_seen.content, collapse("""
-            \x0314{}: Command \x02spam\x02 encountered an error: lorem
-            ipsum.""".format(self.other_user.nick)))
+            \x0314{}: Lorem ipsum.""".format(self.other_user.nick)))
 
     def test_empty_buffer(self):
         self.more()