runtime error in `from_public_link` when port is not 80

[HengyueLi]

consider the placement with:

    @classmethod
    def from_public_link(cls, public_link, folder_password='', **kwargs):
        public_link_components = parse.urlparse(public_link)
        url = public_link_components.scheme + '://' + public_link_components.hostname
        if public_link_components.port:
            url += ":" + str(public_link_components.port)
        folder_token = public_link_components.path.split('/')[-1]
        anon_session = cls(url, **kwargs)
        anon_session.anon_login(folder_token, folder_password=folder_password)
        return anon_session