PIM-3377: Check if locale specific exists in attribute dunring import

TODO:

- [x] Fix the behat
- [x] Add a check on import (see jira tiket PIM-3377)
- [x] Add a check on export (see jira tiket PIM-3377)

| Q                    | A
| -------------------- | ---
| Bug fix?             | Yes
| New feature?         | No
| BC breaks?           | No
| CI currently passes? | Yes
| Tests pass?          | Running
| Scenarios pass?      | Running
| Checkstyle issues?*  | No
| PMD issues?**        | No
| Changelog updated?   | Yes
| Fixed tickets        | PIM-3377
| Doc PR               | -
why do you iterate on `$attribute->getAvailableLocales()` ? you can just use it directly, no ?