def authenticate(self, username=None, password=None, api_key=None,
            tenant_id=None, connect=False):
        """
        Using the supplied credentials, connects to the specified
        authentication endpoint and attempts to log in.

        Credentials can either be passed directly to this method, or
        previously-stored credentials can be used. If authentication is
        successful, the token and service catalog information is stored, and
        clients for each service and region are created.

        The 'connect' parameter is retained for backwards compatibility. It no
        longer has any effect.
        """
        self.username = username or self.username or pyrax.get_setting(
                "username")
        # Different identity systems may pass these under inconsistent names.
        self.password = password or self.password or api_key or self.api_key
        self.api_key = api_key or self.api_key or self.password
        self.tenant_id = tenant_id or self.tenant_id or pyrax.get_setting(
                "tenant_id")
        creds = self._format_credentials()
        headers = {"Content-Type": "application/json",
                "Accept": "application/json",
                }
        resp, resp_body = self.method_post("tokens", data=creds,
                headers=headers, std_headers=False)

        if resp.status_code == 401:
            # Invalid authorization
            raise exc.AuthenticationFailed("Incorrect/unauthorized "
                    "credentials received")
        elif 500 <= resp.status_code < 600:
            # Internal Server Error
            try:
                error_msg = resp_body[list(resp_body.keys())[0]]["message"]
            except (KeyError, AttributeError):
                error_msg = "Service Currently Unavailable"
            raise exc.InternalServerError(error_msg)
        elif resp.status_code > 299:
            try:
                msg = resp_body[list(resp_body.keys())[0]]["message"]
            except (KeyError, AttributeError):
                msg = None
            if msg:
                err = "%s - %s." % (resp.reason, msg)
            else:
                err = "%s." % resp.reason
            raise exc.AuthenticationFailed(err)
        self._parse_response(resp_body)
        self.authenticated = True
Using the supplied credentials, connects to the specified
        authentication endpoint and attempts to log in.

        Credentials can either be passed directly to this method, or
        previously-stored credentials can be used. If authentication is
        successful, the token and service catalog information is stored, and
        clients for each service and region are created.

        The 'connect' parameter is retained for backwards compatibility. It no
        longer has any effect.