This is useful if a post-processing program is unable to understand
absolute non-URI locations, e.g. by interpreting them relative to a
host and erroring out instead of defaulting to the local filesystem,
if no host (base URI) is known.

normpath should already return an absolute path, unless base_path is not
absolute, which would seem like a user error and guessing paths wouldn't
have helped there anyway.

This reverts commit 91c24ec.