Updating DirectoryDoesNotExistException and InvalidBundlableNodeException to accept string filePath params.
The only place this is used is by the BundleDepsCommand, where I've introduced a relativePath string which I normalise to "/" instead of "\\" so that tests don't have to deal with this (File.separators in tests are nasty)
Added missing @Test annotation and fixed the test so that it throws the intended exception (needed the app to exist first)
Misc: Removing unused import
cc: @dchambers