Handle Invalid User error coming from madmin (#314)

Right now we display `Internal Server Error` when invalid credentials are presneted, this makes it so we only present `Unauthorized`

restapi/error.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/go-openapi/swag"
 	"github.com/minio/console/models"
+	"github.com/minio/minio/pkg/madmin"
 	k8sErrors "k8s.io/apimachinery/pkg/api/errors"
 )
 
@@ -86,6 +87,11 @@ func prepareError(err ...error) *models.Error {
 			errorCode = 401
 			errorMessage = errorGenericInvalidSession.Error()
 		}
+		// console invalid session error
+		if madmin.ToErrorResponse(err[0]).Code == "XMinioAdminNoSuchUser" {
+			errorCode = 401
+			errorMessage = errorGenericInvalidSession.Error()
+		}
 		// if we received a second error take that as friendly message but dont override the code
 		if len(err) > 1 && err[1] != nil {
 			log.Print("friendly error: ", err[1].Error())