If you use minecraft1.8 at the first time ,the minecraft can't find the resourcepacks folder which is not as same as other versions to create the resourcepacks automaticly.so we have to add the new resourcepack folder to avoid the error when we click "Open resource pack folder" button
PS.the error means windows can't find the resoucepacks folder
This issue is a duplicate of MC-68745. It has been linked to the original bugreport.
Please search before reporting any bugs, as it's likely that one exists already.