ENH: give explicit error
ENH: give explicit error

SiLab-Bonn/testbeam_analysis,YannickDieter/testbeam_analysis,YannickDieter/testbeam_analysis,SiLab-Bonn/testbeam_analysis,SiLab-Bonn/testbeam_analysis,YannickDieter/testbeam_analysis,YannickDieter/testbeam_analysis,SiLab-Bonn/testbeam_analysis