title: Migrations error in django 2; AttributeError: 'str' object has no attribute 'decode'
body: <p>I am running migrations on my newly built app called 'core'. 
  When I run migrations on it, I get an error that tells me this; </p>
  
  <pre><code>query = query.decode(errors='replace')
  AttributeError: 'str' object has no attribute 'decode'
  </code></pre>
  
  <p>I am posting the Traceback below; </p>
  
  <pre><code>C&gt; python manage.py makemigrations core
  Traceback (most recent call last):
    File "manage.py", line 21, in &lt;module&gt;
      main()
    File "manage.py", line 17, in main
      execute_from_command_line(sys.argv)
    File "C:\Python37\lib\site-packages\django\core\management\__init__.py", line 381, in execute_from_command_line
      utility.execute()
    File "C:\Python37\lib\site-packages\django\core\management\__init__.py", line 375, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "C:\Python37\lib\site-packages\django\core\management\base.py", line 323, in run_from_argv
      self.execute(*args, **cmd_options)
    File "C:\Python37\lib\site-packages\django\core\management\base.py", line 364, in execute
      output = self.handle(*args, **options)
    File "C:\Python37\lib\site-packages\django\core\management\base.py", line 83, in wrapped
      res = handle_func(*args, **kwargs)
    File "C:\Python37\lib\site-packages\django\core\management\commands\makemigrations.py", line 101, in handle
      loader.check_consistent_history(connection)
    File "C:\Python37\lib\site-packages\django\db\migrations\loader.py", line 283, in check_consistent_history
      applied = recorder.applied_migrations()
    File "C:\Python37\lib\site-packages\django\db\migrations\recorder.py", line 73, in applied_migrations
      if self.has_table():
    File "C:\Python37\lib\site-packages\django\db\migrations\recorder.py", line 56, in has_table
      return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
    File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 256, in cursor
      return self._cursor()
    File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 233, in _cursor
      self.ensure_connection()
    File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 217, in ensure_connection
      self.connect()
    File "C:\Python37\lib\site-packages\django\db\backends\base\base.py", line 197, in connect
      self.init_connection_state()
    File "C:\Python37\lib\site-packages\django\db\backends\mysql\base.py", line 233, in init_connection_state
      if self.features.is_sql_auto_is_null_enabled:
    File "C:\Python37\lib\site-packages\django\utils\functional.py", line 80, in __get__
      res = instance.__dict__[self.name] = self.func(instance)
    File "C:\Python37\lib\site-packages\django\db\backends\mysql\features.py", line 82, in is_sql_auto_is_null_enabled
      cursor.execute('SELECT @@SQL_AUTO_IS_NULL')
    File "C:\Python37\lib\site-packages\django\db\backends\utils.py", line 103, in execute
      sql = self.db.ops.last_executed_query(self.cursor, sql, params)
    File "C:\Python37\lib\site-packages\django\db\backends\mysql\operations.py", line 146, in last_executed_query
      query = query.decode(errors='replace')
  AttributeError: 'str' object has no attribute 'decode'
  </code></pre>
  
  <p>Here is the Models file;</p>
  
  <pre><code>    class Movie(models.Model):
  
      NOT_RATED = 0
      RATED_G = 1
      RATED_PG = 2
      RATED_R = 3
  
      RATINGS = (
          (NOT_RATED,'NR - Not Rated'),
          (RATED_G, 'G - General Audiences'),
          (RATED_PG, 'PG - Parental Guidance'),
          (RATED_R, 'R - Restricted'),
          )
  
      title = models.CharField(max_length=140)
      plot = models.TextField()
      year = models.PositiveIntegerField()
      rating = models.IntegerField(choices=RATINGS, default=NOT_RATED)
      runtime = models.PositiveIntegerField()
      website = models.URLField(blank=True)
  
      def __str__(self):
          return '{} {}'.format(self.title, self.year)
  </code></pre>
  
  <p>Here is the Settings for the database I am using (MySQL) :</p>
  
  <pre><code>    DATABASES = {
      'default': {
          'ENGINE': 'django.db.backends.mysql',
          'NAME': 'mymdb',
          'USER': '',
          'PASSWORD': '',
          'HOST': '127.0.0.1',
          'PORT': '3306'
      }
  }
  </code></pre>