transformation CLI: always print exception message

Change-Id: Icd41254b1e6e4c2874259e5e27e47fd652f9e7b5
Reviewed-on: http://gerrit.esdi-community.eu/3181
Tested-by: Jenkins <sitemple@igd.fraunhofer.de>
Reviewed-by: Simon Templer <simon.templer@igd.fraunhofer.de>