Fix exception when loading themes and Twig namespaces
Fix exception when loading themes and Twig namespaces

Exception message was:
```
Twig_Error_Loader: Template "@Twig/Exception/exception_full.html.twig"
is not defined (There are no registered paths for namespace "Twig".). at
/Users/lolautruche/workspace/onisep/ezpublish/vendor/twig/twig/lib/Twig/Loader/Chain.php
line 90
```

lolautruche/EzCoreExtraBundle