(PUP-716) Refactor tempfile_spec after FileSystem API change
(PUP-716) Fix up base_spec tests after FileSystem API change
(PUP-716) Fix reference to removed FileSystem::File
(PUP-716) Fix typos after change of FileSystem API

writable? is spelled just like that
A BucketFile is not a Pathname
Removed reference to FileSystem::File