Problem Definition

With the removal of the usernames, username should no longer be a point of reference for CSV import.
The CSV importer still refers back to username to map to the Assignee field.

Steps to Replicate

1. Create a test csv import with the assignee field
2. Use user email to map to the assignee

Expected Result

As mentioned, username should no longer applicable, hence the import should succeed with Assignee value mapped to the email address

Actual Result

The mapping still refers to username instead of email address,

Running import returns error:

issue can't be created due to the error/s user does not exist

Workaround

As an alternative way to get user name for the affected user,

1. As a site admin, launch a browser and access the URL : https://<yoursite>/rest/api/3/user/search?query=<User_Email_Address>
2. The username information will be returned on the self url.
3. Extract this information and replace the email address with the username in the CSV file