Using /producer-\w+ as pattern is incorrect, we have no guarantee that
the canonical repository or gem name will be included in the install
path. Just use /producer pattern to match lib files or executables.
Backtrace filtering was only disabled for exception cause, this change
ensure no backtrace filtering at all in debug mode.
* Prevent main exception filtering when debug mode is enabled;
* Test when exception cause must be displayed;
* Test how exception cause must be displayed.