better error message when KDiff3 couldn't be located
better error message when KDiff3 couldn't be located

rolembergfilho/Serenity,WasimAhmad/Serenity,volkanceylan/Serenity,dfaruque/Serenity,volkanceylan/Serenity,dfaruque/Serenity,rolembergfilho/Serenity,dfaruque/Serenity,WasimAhmad/Serenity,volkanceylan/Serenity,rolembergfilho/Serenity,dfaruque/Serenity,volkanceylan/Serenity,rolembergfilho/Serenity,WasimAhmad/Serenity,WasimAhmad/Serenity,dfaruque/Serenity,volkanceylan/Serenity,WasimAhmad/Serenity,rolembergfilho/Serenity