Error on importing multiple users with same username

Problem/Motivation

Importing users with same username gives an error:

Integrity constraint violation: 1062 Duplicate entry 'john-en' for key 'user__name': INSERT INTO "users_field_data"

Steps to reproduce

1. Select multiple fields to import. I selected name, mail and 4 other fields.
2. Generate the sample csv file.
3. Import the sample file.
4. Change the mail ID for one of the users in the csv file(the username should remain the same) and import.