more explicit error message
more explicit error message


Former-commit-id: ab62b88281713c3d7fc717fd593ab3aeaa7f2877
Anatoscope/sofa,Anatoscope/sofa,Anatoscope/sofa,Anatoscope/sofa,FabienPean/sofa,Anatoscope/sofa,hdeling/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,Anatoscope/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,hdeling/sofa,FabienPean/sofa,hdeling/sofa,Anatoscope/sofa,hdeling/sofa,Anatoscope/sofa,FabienPean/sofa,FabienPean/sofa,hdeling/sofa,FabienPean/sofa,Anatoscope/sofa