moin openid plugin doesn't respect timezones

[Andrew Glen-Young]

If moin-openid is configured to ask for timezones, the user's timezone offset is calculated incorrectly if the user is not within the server's timezone.

The incorrect calculation seems to occur within the '_handle_verify_continuation' function in the openidrp.py module.

Example:

If I login to a wiki with my timezone set to Europe/London (which is the same as the server's timezone) my timezone offset is correctly calculated as zero.

If I change my timezone to Europe/Lisbon, logout and log back into the wiki, my timezone offset is incorrectly set to -2320 (user_tz: Europe/Lisbon, user_utcoffset: -1 day, 23:23:00)