An exception that will turn into an HTTP error response.
Raising an `HTTPError` is a convenient alternative to calling
`RequestHandler.send_error` since it automatically ends the
current function.
To customize the response sent with an `HTTPError`, override
`RequestHandler.write_error`.
:arg int status_code: HTTP status code. Must be listed in
`httplib.responses <http.client.responses>` unless the ``reason``
keyword argument is given.
:arg string log_message: Message to be written to the log for this error
(will not be shown to the user unless the `Application` is in debug
mode). May contain ``%s``-style placeholders, which will be filled
in with remaining positional parameters.
:arg string reason: Keyword-only argument. The HTTP "reason" phrase
to pass in the status line along with ``status_code``. Normally
determined automatically from ``status_code``, but can be used
to use a non-standard numeric code.
Definition at line 1921 of file web.py.
