Steps to reproduce:
1. Open QA attached project "AssetBundleTest.zip"
2. Open script inside Editor folder
3. Inspect that Asset is marked twice for the same bundle
4. In the Editor, press Assets -> Build Bundle
5. Error message states "Asset "Assets/GameObject 11.prefab" has been marked into more than one AssetBundles."

Expected: In such a case, the error message should state that the Asset is marked into the same bundle multiple times
Actual: The error makes it seem like the Asset has been marked into different bundles somewhere misleading the user when troubleshooting

Reproduced on: 5.5.4p1, 5.6.0f3, 2017.1.0p1, 2017.2.0b4, 2017.3.0a1