gists: handle 500 error on sending unsupported format

rhodecode/apps/gist/views.py

@@ -25,7 +25,7 b' import formencode'
 import formencode.htmlfill
 import peppercorn
 
-from pyramid.httpexceptions import HTTPNotFound, HTTPFound
+from pyramid.httpexceptions import HTTPNotFound, HTTPFound, HTTPBadRequest
 from pyramid.view import view_config
 from pyramid.renderers import render
 from pyramid.response import Response
@@ -295,6 +295,8 b' class GistView(BaseAppView):'
             response = Response(content)
             response.content_type = 'text/plain'
             return response
+        elif return_format:
+            raise HTTPBadRequest()
 
         return self._get_template_context(c)