inspectalerts: improve error message when no bearer token is available

When using certificate-based authentication (e.g. system:admin from
installer kubeconfig), the monitoring API on Thanos Querier rejects
the request because kube-rbac-proxy only supports TokenReview-based
authentication on the web port (9091). The previous error message
("no token is currently in use for this session") did not explain
why it failed or what the user should do.

Update the message to clarify that token-based auth is required and
point users to 'oc login'

Signed-off-by: Daniel Mellado <dmellado@fedoraproject.org>

Author: danielmellado

pkg/cli/admin/inspectalerts/inspectalerts.go

@@ -99,7 +99,7 @@ func (o *options) Run(ctx context.Context) error {
 // other forms of authentication.
 func ValidateRESTConfig(restConfig *rest.Config) error {
 	if restConfig.BearerToken == "" && restConfig.BearerTokenFile == "" {
-		return fmt.Errorf("no token is currently in use for this session")
+		return fmt.Errorf("no bearer token available for this session; the monitoring API requires token-based authentication, use 'oc login'")
 	}
 	return nil
 }