Rather than having int() raise a ValueError that doesn't explain what is
going on, re-raise with a new description.

docs/news.txt

@@ -7,10 +7,15 @@ Unreleased
Backwards Incompatibilities
~~~~~~~~~~~~~~~~~~~~~~~~~~~

- ``response.set_cookie`` renamed the only required parameter from "key" to
- ``Response.set_cookie`` renamed the only required parameter from "key" to
  "name". The code will now still accept "key" as a keyword argument, and will
  issue a DeprecationWarning until WebOb 1.7.

- The ``status`` attribute of a ``Response`` object no longer takes a string
  like ``None None`` and allows that to be set as the status. It now has to at
  least match the pattern of ``<integer status code> <explenation of status
  code>``. Invalid status strings will now raise a ``ValueError``.

1.5.0a0 (2015-07-25)
--------------------

@@ -38,7 +43,7 @@ Backwards Incompatibilities
  RFC6265 suggests using base 64 to serialize data before storing data in a
  cookie.

- ``response.set_cookie`` now uses the internal ``make_cookie`` API, which will
- ``Response.set_cookie`` now uses the internal ``make_cookie`` API, which will
  issue warnings if cookies are set with invalid bytes. See
  https://github.com/Pylons/webob/pull/172

webob/response.py

@@ -262,7 +262,10 @@ def _status__set(self, value):
                % type(value))

        # Attempt to get the status code itself, if this fails we should fail
        status_code = int(value.split()[0])
        try:
            status_code = int(value.split()[0])
        except ValueError:
            raise ValueError('Invalid status code, integer required.')
        self._status = value

    status = property(_status__get, _status__set, doc=_status__get.__doc__)