Timezone does not set

[ivanff]

Checklist

• I have verified that that issue exists against the master branch of Django REST framework.
• I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
• This is not a usage question. (Those should be directed to the discussion group instead.)
• This cannot be dealt with as a third party library. (We prefer new functionality to be in the form of third party libraries where possible.)
• I have reduced the issue to the simplest possible case.
• I have included a failing test as a pull request. (If you are unable to do so we can still accept the issue.)

Steps to reproduce

DateTimeField
...

def to_representation(self, value):
    if not value:
        return None

    output_format = getattr(self, 'format', api_settings.DATETIME_FORMAT)

    if output_format is None or isinstance(value, six.string_types):
        return value

    if output_format.lower() == ISO_8601:
        value = self.enforce_timezone(value)
        value = value.isoformat()
        if value.endswith('+00:00'):
            value = value[:-6] + 'Z'
        return value
    return value.strftime(output_format)

Expected behavior

Actual behavior

Timezone does not set (self.enforce_timezone(value)) for non ISO_8601 formatsd

[carltongibson]

Was fixed in #5833. (Please see item 1 of the issue template checklist.)