The package is severely out of date with respect to the Debian
Policy. Latest version is 4.6.2
and your package only follows
3.9.4...
The package has a debian/watch file, but the last attempt
to use it for checking for newer upstream versions failed with
an error:
In watchfile debian/watch, reading webpage http://home.ccil.org/~cowan/XML/tagsoup/ failed: 500 Can't connect to home.ccil.org:80 (Name or service not known)