When a GET request is sent to a resource which (generally for security reasons) requires POST, an appropriate response code should be sent, so that clients such as python-jenkins may properly report the error.

• Most such web methods use @RequirePOST, for which currently a 500 is sent because org.kohsuke.stapler.interceptor.RequirePOST$Processor simply throws IllegalAccessException.
• Build-like requests use BuildAuthorizationToken which forwards to requirePOST.jelly with a 200, which is no good. (If a token is supplied but is incorrect, it more reasonably sends a 403, via AccessDeniedException.)

Both cases should probably send a 405 ("Method Not Allowed") with Allow: POST, though a 403 would not be inappropriate for the latter case since under some circumstances GET is still allowed for compatibility.