deal with expected exceptions when listing tasks
deal with expected exceptions when listing tasks

This resolves the usability part from #226

arcivanov/pybuilder,paolodedios/pybuilder,esc/pybuilder,arcivanov/pybuilder,arcivanov/pybuilder,pybuilder/pybuilder,paolodedios/pybuilder,paolodedios/pybuilder,pybuilder/pybuilder,pybuilder/pybuilder,esc/pybuilder,esc/pybuilder