Password reset returns an exception if the key parameter is missing

[amercader]

Instead of showing a notice, the password reset page throws an exception if the key parameter is missing:

Module ckan.controllers.user:329 in perform_reset
         c.reset_key = request.params.get('key')
               if not mailer.verify_reset_link(user_obj, c.reset_key):
                   h.flash_error(_('Invalid reset key. Please try again.'))
                   abort(403)
 if not mailer.verify_reset_link(user_obj, c.reset_key):
Module ckan.lib.mailer:100 in verify_reset_link
     if not user.reset_key or len(user.reset_key) < 5:
               return False
           return key.strip() == user.reset_key
 return key.strip() == user.reset_key
AttributeError: 'NoneType' object has no attribute 'strip'

Apart from the obvious fix of checking for the 'key' parameter, it seems like is quite common to get these reset urls without the key parameter, so I suspect some email clients might strip the query params when building the links. We could avoid this problem by making the key part of the url instead of a param:

​http://thedatahub.org/en/user/reset/3086e91c-fe09-4a98-92e1-19de67a9ac9d/b4c2d03fa8

instead of:

​http://thedatahub.org/en/user/reset/3086e91c-fe09-4a98-92e1-19de67a9ac9d?key=b4c2d03fa8