All reports of gz-file-not-gzip for the archive. The extended description of this tag is:

The given file ends with .gz, which normally indicates it is compressed with gzip. However, it doesn't seem to be a gzip-compressed file. gzip will fail with an error on such files. Normally this indicates a mistake in the installation process of the package.

Severity: normal, Certainty: possible

Check: files, Type: binary, udeb

This tag has not been emitted in any package tested by Lintian.