Add '+' so multi-line error formatting is consistent
Add '+' so multi-line error formatting is consistent

quantopian/datashape,blaze/datashape,FrancescAlted/datashape,aterrel/datashape,FrancescAlted/datashape,cpcloud/datashape,cpcloud/datashape,llllllllll/datashape,ContinuumIO/datashape,cowlicks/datashape,blaze/datashape,cowlicks/datashape,ContinuumIO/datashape,quantopian/datashape,aterrel/datashape,llllllllll/datashape