<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def errcat(self):
        '''
        List the posts to be modified.
        '''
        post_recs = MPost.query_random(limit=1000)
        outrecs = []
        errrecs = []
        idx = 0
        for postinfo in post_recs:
            if idx > 16:
                break
            cat = MPost2Catalog.get_first_category(postinfo.uid)
            if cat:
                if 'def_cat_uid' in postinfo.extinfo:
                    if postinfo.extinfo['def_cat_uid'] == cat.tag_id:
                        pass
                    else:
                        errrecs.append(postinfo)
                        idx += 1
                else:
                    errrecs.append(postinfo)
                    idx += 1
            else:
                outrecs.append(postinfo)
                idx += 1
        self.render('list/errcat.html',
                    kwd={},
                    norecs=outrecs,
                    errrecs=errrecs,
                    userinfo=self.userinfo)