write status to status.txt

def show(self, f, pattern=None):
        '''write status to status.txt'''
        if pattern is None:
            f.write('Counters: ')
            for c in self.counters:
                f.write('%s:%s ' % (c, self.counters[c]))
            f.write('\n')
            f.write('MAV Errors: %u\n' % self.mav_error)
            f.write(str(self.gps)+'\n')
        for m in sorted(self.msgs.keys()):
            if pattern is not None and not fnmatch.fnmatch(str(m).upper(), pattern.upper()):
                continue
            f.write("%u: %s\n" % (self.msg_count[m], str(self.msgs[m])))