      outputs = {
          datetime.datetime(2001, 1, 1, 13, 00): '2001-01-01T13:00:00Z',
          datetime.datetime(2001, 1, 1, 13, 00, tzinfo=utc): '2001-01-01T13:00:00Z',
          '2001-01-01T00:00:00': '2001-01-01T00:00:00',
          six.text_type('2016-01-10T00:00:00'): '2016-01-10T00:00:00',
          None: None,
          '': None,
      }
      field = serializers.DateTimeField(default_timezone=utc)
  
 
</s> remove         six.text_type('2016-01-10'): '2016-01-10',
 </s> add         str('2016-01-10'): '2016-01-10', </s> remove         assert isinstance(self.pagination.to_html(), six.text_type)
 </s> add         assert isinstance(self.pagination.to_html(), str) </s> remove         assert field.run_validation(1) is 1
 </s> add         assert field.run_validation(1) == 1 </s> remove         assert serializer.errors == {'target': ['Incorrect type. Expected pk value, received %s.' % six.text_type.__name__]}
 </s> add         assert serializer.errors == {'target': ['Incorrect type. Expected pk value, received str.']} </s> remove       - { python: "2.7", env: TOXENV=lint }
      - { python: "2.7", env: TOXENV=docs }
 </s> add       - { python: "3.7", env: TOXENV=lint }
      - { python: "3.7", env: TOXENV=docs }
        str('2016-01-10T00:00:00'): '2016-01-10T00:00:00',
      outputs = {
          datetime.datetime(2001, 1, 1, 13, 00): '2001-01-01T13:00:00Z',
          datetime.datetime(2001, 1, 1, 13, 00, tzinfo=utc): '2001-01-01T13:00:00Z',
          '2001-01-01T00:00:00': '2001-01-01T00:00:00',
        str('2016-01-10T00:00:00'): '2016-01-10T00:00:00',
          None: None,
          '': None,
      }
      field = serializers.DateTimeField(default_timezone=utc)
  
keep keep keep keep replace keep keep keep keep keep
 Dropped Python 2 compatibility. (#6615)

Thanks to Jon Dufresne (@jdufresne) for review.

Co-authored-by: Asif Saif Uddin <auvipy@gmail.com>
Co-authored-by: Rizwan Mansuri <Rizwan@webbyfox.com> 
tests/test_fields.py