better error output if a project is not found
better error output if a project is not found

paulovieira/tilemill-clima,MappingKat/tilemill,mbrukman/tilemill,MappingKat/tilemill,Zhao-Qi/tilemill,Zhao-Qi/tilemill,nyimbi/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,MappingKat/tilemill,mbrukman/tilemill,florianf/tileoven,Teino1978-Corp/Teino1978-Corp-tilemill,nyimbi/tilemill,tilemill-project/tilemill,paulovieira/tilemill-clima,tizzybec/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,paulovieira/tilemill-clima,mbrukman/tilemill,nyimbi/tilemill,paulovieira/tilemill-clima,nyimbi/tilemill,tizzybec/tilemill,florianf/tileoven,tilemill-project/tilemill,mbrukman/tilemill,fxtentacle/tilemill,Zhao-Qi/tilemill,tizzybec/tilemill,fxtentacle/tilemill,tizzybec/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,MappingKat/tilemill,nyimbi/tilemill,Teino1978-Corp/Teino1978-Corp-tilemill,florianf/tileoven,tizzybec/tilemill,Zhao-Qi/tilemill,mbrukman/tilemill,tilemill-project/tilemill,fxtentacle/tilemill,Zhao-Qi/tilemill,MappingKat/tilemill,fxtentacle/tilemill,fxtentacle/tilemill,paulovieira/tilemill-clima