Error message while adding in a group without authorization is incorrect in English

Pre-conditions
User should have Admin permissions
Steps to reproduce
1. Open "Users" page and search for any existed user with groups
2. Open groups multi select box
3. Log out in another tab
4. Add any group from the list
Actual result
Error message "Error on add group" is shown
Expected result
Error message "An error occurred while adding in a group" is shown