def get_user(uid):
    """ Returns a user from the DCOS Enterprise.  It returns None if none exists.

        :param uid: user id
        :type uid: str
        :return: User
        :rtype: dict
    """
    try:
        acl_url = urljoin(_acl_url(), 'users/{}'.format(uid))
        r = http.get(acl_url)
        return r.json()
        # assert r.status_code == 201
    except DCOSHTTPException as e:
        if e.response.status_code == 400:
            return None
        else:
            raise