'Rolls back the transaction if one is in progress.'

def Rollback(self, force_rollback=False):

    if (not self.in_transaction):
        return
    msg = 'Rolling    back    the    update.'
    if (self.config.vm and (not force_rollback)):
        msg += '        This    can    sometimes    take    a    while    since    a    VM    version    is    being    rolled    back.'
    StatusUpdate(msg, self.error_fh)
    self.logging_context.Send('/api/appversion/rollback', force_rollback=('1' if force_rollback else '0'))
    self.in_transaction = False
    self.files = {}
