def _really_parse_tag(self):
        """Actually parse an HTML tag, starting with the open (``<foo>``)."""
        data = _TagOpenData()
        self._push(contexts.TAG_OPEN)
        self._emit(tokens.TagOpenOpen())
        while True:
            this, next = self._read(), self._read(1)
            can_exit = (not data.context & (data.CX_QUOTED | data.CX_NAME) or
                        data.context & data.CX_NOTE_SPACE)
            if this is self.END:
                if self._context & contexts.TAG_ATTR:
                    if data.context & data.CX_QUOTED:
                        # Unclosed attribute quote: reset, don't die
                        data.context = data.CX_ATTR_VALUE
                        self._memoize_bad_route()
                        self._pop()
                        self._head = data.reset
                        continue
                    self._pop()
                self._fail_route()
            elif this == ">" and can_exit:
                self._handle_tag_close_open(data, tokens.TagCloseOpen)
                self._context = contexts.TAG_BODY
                if is_single_only(self._stack[1].text):
                    return self._handle_single_only_tag_end()
                if is_parsable(self._stack[1].text):
                    return self._parse(push=False)
                return self._handle_blacklisted_tag()
            elif this == "/" and next == ">" and can_exit:
                self._handle_tag_close_open(data, tokens.TagCloseSelfclose)
                return self._pop()
            else:
                self._handle_tag_data(data, this)
            self._head += 1