Warcserver / CDXJ API: properly handle unsupported output formats (#623)

- add unit test to verify unknown output formats are handled
  if output fields param is in request

pywb/warcserver/handlers.py

@@ -86,7 +86,7 @@ def __call__(self, params):
         if fields and isinstance(fields, str):
             fields = fields.split(',')
 
-        handler = self.OUTPUTS.get(output, fields)
+        handler = self.OUTPUTS.get(output)
         if not handler:
             errs = dict(last_exc=BadRequestException('output={0} not supported'.format(output)))
             return None, None, errs

tests/test_cdx_server_app.py

@@ -287,5 +287,13 @@ def test_collapseTime_resolveRevisits_reverse(self):
         for i in range(len(cdxes) - 1):
             assert cdxes[i]['timestamp'] >= cdxes[i + 1]['timestamp']
 
+    def test_error_unknown_output_format(self):
+        """test unknown output format in combination with a list of output fields"""
+        resp = self.query('http://www.iana.org/_css/2013.1/print.css',
+                          is_error=True,
+                          fields='urlkey,timestamp,status',
+                          output='foo')
+        assert resp.status_code == 400
+        assert resp.json == {'message': 'output=foo not supported'}