Raised by ImagePipe.Plug when a response fails after its 200 status and
headers were sent.
The response can't become an error response at that point. Over HTTP/1.1,
raising makes the server close the connection without completing the body,
so clients and CDNs see the response as truncated rather than complete. ImagePipe has
already logged the underlying failure. Its status is 500.
Over HTTP/2 with Bandit, ImagePipe.Plug raises Bandit's
Bandit.HTTP2.Errors.StreamError instead, so that Bandit resets the stream.