Add HTTP status code to request assertion message.

Following an http request, simple tests asserts that content was downloaded, and uses the following assertion message:

POST to http://example.com/, response is 49121 bytes.

I'm fairly new to Simpletest, and just spent some time troubleshooting one of my module's tests. I was trying to set a form field, but kept getting an "unable to set field"-message. Since the request assertion was shown in green and with a number of bytes downloaded, my poor brain was misled into thinking that the correct page was loaded. If I'd had the status code, I'd seen the 403 (access denied) message.

IMHO, the HTTP status code for the request is at least as important as the number of bytes downloaded. I'd like to see the message change to:

POST to http://example.com/, status is 403, response is 49121 bytes.

Any takers?