Pull request: No feedback is provided when the user enter wrong names in the reviewer search input field

Issue Summary

When the user searches for a user in the "Reviewers" search input field, when no user is found in the list, there is no indication of the same for the assistive technology users.

Steps to Reproduce

1. Navigate to the Reviewer link and activate it
2. Start typing any user name.

Screen recording

Screen Recording 2022-04-18 at 3.26.39 PM.mov

Actual Results

In the "Reviewers" search input field when the user tries to search for the user and no user is found for the desired input, there is no indication for error message whether the user is available or not. The lack of textual error messages makes it difficult for users (especially users who are blind or have learning disabilities) to recognise the presence of errors, identify the cause of the problem and understand how to solve it.

Expected Results

An error message should be announced or loaded on the page to indicate to the assistive technology user that no such user is found for reviewers. Error messages must clearly describe the problem that has occurred and includes suggestions (wherever possible) on how to rectify it. It is a good practice to display error messages using red colour.

Workaround

Currently, there is no known workaround for this behaviour. A workaround will be added here when available