All reports of missing-debian-source-format for the archive. The extended description of this tag is:
Explicitly selecting a source format by putting the format in debian/source/format is recommended. This allows for future removal of the 1.0 default for the package source format and, depending on the source format, may allow unambiguous declaration of whether this package is native or non-native.
If you don't have a reason to stay with the old format for this package, please consider switching to "3.0 (quilt)" (for packages with a separate upstream tarball) or to "3.0 (native)" (for Debian native packages).
If you wish to keep using the old format, please create that file and put "1.0" in it to be explicit about the source package version. If you have problems with the 3.0 format, the dpkg maintainers are interested in hearing, at firstname.lastname@example.org, the (technical) reasons why the new formats do not suit you.
Refer to the dpkg-source(1) manual page and https://wiki.debian.org/Projects/DebSrc3.0 for details.
This tag has not been emitted in any package tested by Lintian.