def case_study_social_link_twitter(value):
    """
    Confirms that the social media url is pointed at the correct domain.

    Args:
        value (string): The url to check.

    Raises:
        django.forms.ValidationError

    """

    parsed = parse.urlparse(value.lower())
    if not parsed.netloc.endswith('twitter.com'):
        raise ValidationError(MESSAGE_NOT_TWITTER)