Add output in why-not for when a package requires a platform package and it is not found, fixes #5259
Add output in why-not for when a package requires a platform package and it is not found, fixes #5259

davidolrik/composer,alcohol/composer,balbuf/composer,pierredup/composer,MoT3rror/composer,yaman-jain/composer,andrerom/composer,staabm/composer,phansys/composer,JBleijenberg/composer,slbmeh/composer,nicolas-grekas/composer,remicollet/composer,hirak/composer,gencer/composer,till/composer,fabpot/composer,stof/composer,dzuelke/composer,floverdevel/composer,curry684/composer,fabiang/composer,localheinz/composer,vdm-io/composer,erasys/composer,milleruk/composer,stefangr/composer,jreinke/composer,SpacePossum/composer,johnstevenson/composer,naderman/composer,composer/composer