DEP-5 and public domain

[Colin Watson <cjwatson@debian.org>]

base-passwd ships passwd.master and group.master files which are
intentionally public domain.  I received a bug report
(https://bugs.launchpad.net/ubuntu/+source/base-passwd/+bug/610108)
noting that "License: PD" isn't valid in DEP-5.  Ideally, I'd like to
say something like "Copyright: PD" and omit the License field, but of
course the License field is currently always required.

Would it be possible to make the License field optional in the case of
"Copyright: PD", or is there some other better change that should be
made to accommodate this?

Thanks,

-- 
Colin Watson                                       [cjwatson@debian.org]