Username in UsernameNotFoundException message data
feature #10427 Username in UsernameNotFoundException message data (maryo)

This PR was squashed before being merged into the 2.6-dev branch (closes #10427).

Discussion
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Username in UsernameNotFoundException message data

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

Added username in UsernameNotFoundException message data

Commits
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3dfaa19 Username in UsernameNotFoundException message data