Fixed an aggregation test failure on MySQL.

import datetime

from decimal import Decimal

import re

from django.db import connection

from django.db.models import Avg, Sum, Count, Max, Min

            self.assertEqual(len(captured_queries), 1)

            qstr = captured_queries[0]['sql'].lower()

            self.assertNotIn('for update', qstr)

            forced_ordering = connection.ops.force_no_ordering()

            if forced_ordering:

                # If the backend needs to force an ordering we make sure it's

                # the only "ORDER BY" clause present in the query.

                self.assertEqual(

                    re.findall(r'order by (\w+)', qstr),

                    [', '.join(forced_ordering).lower()]

                )

            else:

                self.assertNotIn('order by', qstr)

            self.assertEqual(qstr.count(' join '), 0)