When the Issue Key does not exist, the Test Case Import fails with a generic error (error importing tests)

Short Description: When the Issue Key does not exist, the Test Case Import fails with a generic error (error importing tests).

Steps to Reproduce:

1 - Go to Test Case Importer via CSV.

2 - Upload the file in attach (make sure the issue key does not exist in jira).

3 - Map the necessary fields.

Actual Results: the import fails with a generic error.

Expected Results: the import should failed with a specific error.