fix: retry_after should be a string.

It's only used as the parameter for "%s", so either string or integer
would work. But keep the type consistent as a string.

Also replace hardcoded string with the variable.

Author: rouilj

roundup/rest.py

@@ -2086,8 +2086,8 @@ def dispatch(self, method, uri, input):
                     # limitStatus. So report a 1 second delay back
                     # to the client. We treat update as sole
                     # source of truth for exceeded rate limits.
-                    retry_after = 1
-                    self.client.setHeader('Retry-After', '1')
+                    retry_after = '1'
+                    self.client.setHeader('Retry-After', retry_after)
 
                 msg = _("Api rate limits exceeded. Please wait: %s seconds.") % retry_after
                 output = self.error_obj(429, msg, source="ApiRateLimiter")