facebook/tornado — pull request #857 by nikitinsm (2013-07-17 14:24:29+00:00)
Title: Client request failed if server answered without reason in status line

"Reason" in http status line is optional

The reason phrases defined in the HTTP specifications (for example, "Not Found" or "Bad Request") are recommended but optional. The HTTP/1.1 specification says that the reason phrases for each status code may be replaced by local equivalents.