I've been fighting we a particular RSS Feed platform returning an "internal server error" message from an exception.

After commenting every try/catch I could find in the stack, I finally had the message from Guzzle saying "405: Method not allowed". Turns out, this provider doesn't accept HEAD requests.

So first thing, "internal server error", the message for a ServerErrorException, sent in HTTP/Client, should not be the default case.

Also, I don't seem to be able to avoid using the HEAD method method in the Reader class, $modifiedSince is forced to be defined and will trigger a HEAD request in Http/Client::getResponse();