All reports of upstream-metadata-is-not-a-file for the archive. The extended description of this tag is:
The DEP 12 metadata file in the source is not readable. This could be caused by a dangling symlink, or that the name is used by some non-file directory entry.
Refer to https://dep-team.pages.debian.net/deps/dep12/ for details.
This tag has not been emitted in any package tested by Lintian.