When trying to add an URL alias to a node (content/urlalias/) where the same URL alias already exists in another language, the following error message is produced: The URL alias <</xxx>> already exists, and it points to <<content/view/full/xxx>>. As it is an alias for another language, it should be created anyway. Automatically generated aliases do not suffer from it and are created correctly even if they are the same (see attached screenshot).

Steps to reproduce:

1. Create fresh eZ Publish 5.4.9 installation with two languages configured (for example "English (United Kingdom)" and "Polish").
2. Create a new object (for example article with name "Test article in two languages").
3. Enter "Manage URL Aliases" for created object (from context menu or by going to /content/urlalias/<id>).
4. Under the "Create new alias" set "URL alias name:" to "/test" and "Language:" to the first language (for example "English (United Kingdom)"). Click "Create" button. The URL alias will be created as expected.
5. Under the "Create new alias" set "URL alias name:" to "/test" and "Language:" to the second language (for example "Polish"). Click "Create" button. The error message will appear: "The URL alias <</test>> already exists, and it points to <<content/view/full/63>>" (see attached screenshot).