||Read the active build config and return the relevant doc paths.
The return value is cached so re-generating with the same docdir won't
invoke the build system a second time.
||Find all files suitable for distributing.
Given the path to generated Sphinx documentation, returns an iterable
of (path, BaseFile) for files that should be archived, uploaded, etc.
Paths are relative to given root directory.
||This function creates an aws session that is
shared between upload and delete both.