twisted.web generates 501 for "unsupported" methods, but it should never do this

[glyph]

 RFC 2616:

10.5.2 501 Not Implemented

The server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource.

(emphasis mine)

Given that twisted.web handles requests on a per-resource basis, extension methods may well be supported by other resources on the server. There's no way that we can know while handling one particular resource what the entire rest of the server may or may not support.

In this case it seems like the server should maybe generate a NOT_ALLOWED, or maybe even a SERVER_ERROR.

[jknight]

web2 returns NOT_ALLOWED; see t.web2.resource.RenderMixin.renderHTTP.