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
-------

3dfaa19 Username in UsernameNotFoundException message data

1 files changed, 8 insertions, 0 deletions

diff --git a/Core/Exception/UsernameNotFoundException.php b/Core/Exception/UsernameNotFoundException.php
index 11607d3..8b72dc2 100644
--- a/Core/Exception/UsernameNotFoundException.php
+++ b/Core/Exception/UsernameNotFoundException.php
@@ -69,4 +69,12 @@ class UsernameNotFoundException extends AuthenticationException
 
         parent::unserialize($parentData);
     }
+
+    /**
+     * {@inheritDoc}
+     */
+    public function getMessageData()
+    {
+        return array('{{ username }}' => $this->username);
+    }
 }