API Gateway 10.1 and higher versions have a different HTTP status response when compared with the previous versions.
Due to an HTTP library upgrade, HTTP response status codes now exclude reason phrases as the default.
Prior to GW 10.1 CR1, the Gateway response would send an HTTP Response Message that contained a status line comprised of the following values:
status-line = HTTP-version SP status-code SP reason-phrase CRLF (Example: HTTP/1.1 200 OK).
With Gateway 10.1 CR1 the reason phrase is no longer included based on the following RFC 7230#section-3.1.2 comments:
As noted in the RFC, the client should not expect this reason phrase as a result the latest HTTP libraries removed this reason phrase.