Lintian tag information: copyright-refers-to-versionless-license-file (type: warning)

Description (from lintian-explain-tags)

The copyright file refers to the versionless symlink in
/usr/share/common-licenses for the full text of the GPL, LGPL, or GFDL
license, but the package does not appear to allow distribution under later
versions of the license. This symlink will change with each release of a
new version of the license and may therefore point to a different version
than the package is released under. debian/copyright should instead refers
to the specific version of the license that the package references.

For example, if the package says something like "you can redistribute it
and/or modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; version 2 dated June, 1991,"
the debian/copyright file should refer to
/usr/share/common-licenses/GPL-2, not /GPL.

Visibility: warning
Show-Always: no
Check: debian/copyright

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