[FrameworkBundle] improved controller name parse error message
feature #11314 [FrameworkBundle] Improved controller class error (jskvara)

This PR was merged into the 2.6-dev branch.

Discussion
----------

[FrameworkBundle] Improved controller class error

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | https://github.com/symfony/symfony/issues/11304
| License       | MIT
| Doc PR        |

Commits
-------

da41eb1 [FrameworkBundle] improved controller name parse error message