While doing the tests I encountered an edge case where a package owned
by the dotfile could be passed either a 'private or 'local location
which is ambiguous (moreover where do we put packages with 'local
location ?).
We remove the ambiguity by removing the 'private value and push the
path ~/.emacs.d/private/local/pkg/ when the owner of a local
package PKG is the dotfile.
When the owner of a local package is a layer then the load path is
in the "local" subdirectory of the layer directory. It adds no value
to use the old 'private location in this case.