callable returned from start_response ignored data passed to it in threaded mode

[rdw]

This bug is pretty obvious if you look at the class ExecuteInThreadPool. There it wraps start_response with this:

    def _start_response(status, headers, exc_info=None):
        head[:] = status, headers, exc_info
        return body.append

body is not used outside of this code, though, so any application that tries to write to the callable will have its data ignored.