Join time string.

def process_formdata(self, valuelist):
        """Join time string."""
        if valuelist:
            time_str = u' '.join(valuelist)
            try:
                timetuple = time.strptime(time_str, self.format)
                self.data = datetime.time(*timetuple[3:6])
            except ValueError:
                self.data = None
                raise