[WIP] PIM-3209: Import is running when we use upload and import with a file with wrong extension

| Q                    | A
| -------------------- | ---
| Bug fix?             | Yes
| New feature?         | No
| BC breaks?           | No
| CI currently passes? | Running
| Tests pass?          | Running
| Scenarios pass?      | Running
| Checkstyle issues?*  | No
| PMD issues?**        | No
| Changelog updated?   | No
| Fixed tickets        | PIM-3209
| DB schema updated?   | No
| Migration script?    | No
| Doc PR               | No
very confusing to have a fileError property and a fileError variable at the same time