Python's BaseHTTPRequestHandler.send_error() is used when you want to report an HTTP error back to the browser. It takes an HTTP error code, and optional description text.
It has a table of default descriptions for all well-known codes. Hence, we shouldn't be duplicating those, as we're just likely to have worse or unfamiliar versions. Unfortunately, that is the case in some parts of the code.
An exception is when we can provide more details. E.g., for code 400 we might be able to be more specific about what in the request is incorrect.
The current offenders are:
* thinlinc.tlwebadm.server (gray area)