Adding same Custom URL Alias for the Content but with different Language fails with an Error message (for test/home URL):
Argument '$path' is invalid: Path 'test/home' already exists for the given language

Step to reproduce
1. Clean eZ Platform 2.5 installation

2. Add a new Language: Polish (pol-PL))

3. For Home add a Polish translation - publish it.

4. Go to URL tab for Home Content. Click on "Add Custom URL" button. In the dialog set:

URL: /test/home
Language: English

Click on "Create" button.

5. Go to URL tab for Home Content. Click on "Add Custom URL" button. In the dialog set:

URL: /test/home
Language: Polish

Click on "Create" button.

Result
Creation of Custom URL alias for the Polish language fails with an Error message:
Argument '$path' is invalid: Path 'test/home' already exists for the given language

Expected result
Custom URL alias is created normally.