Indicate failure when no moderator invite is found.

r2/r2/controllers/api.py

@@ -725,6 +725,8 @@ class ApiController(RedditController, OAuth2ResourceController):
     @api_doc(api_section.subreddits)
     def POST_accept_moderator_invite(self, form, jquery, ip):
         if not c.site.remove_moderator_invite(c.user):
+            c.errors.add(errors.NO_INVITE_FOUND)
+            form.set_error(errors.NO_INVITE_FOUND, None)
             return
 
         ModAction.create(c.site, c.user, "acceptmoderatorinvite")

r2/r2/lib/errors.py

@@ -112,6 +112,7 @@ error_list = dict((
         ('TOO_MANY_DEVELOPERS', _('too many developers')),
         ('BAD_HASH', _("i don't believe you.")),
         ('ALREADY_MODERATOR', _('that user is already a moderator')),
+        ('NO_INVITE_FOUND', _('there is no pending invite for that subreddit')),
         ('BID_LIVE', _('you cannot edit the bid of a live ad')),
         ('TOO_MANY_CAMPAIGNS', _('you have too many campaigns for that promotion')),
         ('BAD_JSONP_CALLBACK', _('that jsonp callback contains invalid characters')),