@abc.abstractmethod<EOL><INDENT>def require_authentication(self, realm, environ):<DEDENT>
raise NotImplementedError<EOL>
Return False to disable authentication for this request.

        This method is called

        - On startup, to check if anonymous access is allowed for a given share.
          In this case, `environ` is None.
        - For every request, before basic or digest authentication is handled.
          If False is returned, we MAY also set environment variables for
          anonymous access::

                environment["wsgidav.auth.roles"] = (<role>, ...)
                environment["wsgidav.auth.permissions"] = (<perm>, ...)
                return False

        Args:
            realm (str):
            environ (dict | None):
        Returns:
            False to allow anonymous access
            True to force subsequent digest or basic authentication