'handler the log records to formatted string'

def logstr(self):

    result = []
    formater = LogFormatter(color=False)
    for record in self.logs:
        if isinstance(record, six.string_types):
            result.append(pretty_unicode(record))
        else:
            if record.exc_info:
                (a, b, tb) = record.exc_info
                tb = hide_me(tb, globals())
                record.exc_info = (a, b, tb)
            result.append(pretty_unicode(formater.format(record)))
            result.append(u'\n')
    return u''.join(result)
