Generate new token on AccessTokenExpired exception

[polsala]

Traceback (most recent call last):
  File "/home/erp/src/erp/server/bin/addons/poweremail/poweremail_mailbox.py", line 57, in run_mail_scheduler
    self.get_all_mail(cursor, user, context={'all_accounts':True})
  File "/home/erp/src/erp/server/bin/addons/poweremail/poweremail_mailbox.py", line 97, in get_all_mail
    core_obj.get_mails(cr, uid, accounts)
  File "/home/erp/src/erp/server/bin/addons/poweremail/poweremail_core.py", line 983, in get_mails
    typ, msg = serv.fetch(str(i), message_parts)
  File "/usr/lib/python2.7/imaplib.py", line 456, in fetch
    typ, dat = self._simple_command(name, message_set, message_parts)
  File "/usr/lib/python2.7/imaplib.py", line 1088, in _simple_command
    return self._command_complete(name, self._command(name, *args))
  File "/usr/lib/python2.7/imaplib.py", line 912, in _command_complete
    raise self.abort('command: %s => %s' % (name, val))
abort: command: FETCH => Session invalidated - AccessTokenExpired