Use a HelpBox instead

Author: donokuda

src/UnityExtension/Assets/Editor/GitHub.Unity/UI/AuthenticationView.cs

@@ -227,17 +227,15 @@ private void ShowMessage()
         {
             if (message != null)
             {
-                GUILayout.Space(Styles.BaseSpacing + 3);
-                GUILayout.Label(message, Styles.CenteredLabel);
-                GUILayout.Space(Styles.BaseSpacing + 3);
+                EditorGUILayout.HelpBox(message, MessageType.Warning);
             }
         }
 
         private void ShowErrorMessage()
         {
             if (errorMessage != null)
             {
-                GUILayout.Label(errorMessage, Styles.ErrorLabel);
+                EditorGUILayout.HelpBox(errorMessage, MessageType.Error);
             }
         }