Fix handling of errors from socket.gethostbyname

Socket functions can raise more than just gaierror. Most of the times,
socket.gethostbyname_ex will return gaierror, but rarely it will also
raise herror. For completeness, we catch all socket exceptions with data
of type (code, description).

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>