[Haskell-cafe] how can we fix our license?

[Ben Franksen]

After uploading a new release i found that this and all our earlier
release show on hackage as "GPL-2.0-only". What we have in our
darcs.cabal is "GPL-2". This was always intended to mean "or later".

I wanted to fix this and upload a new release that uses the new variant
"GPL-2.0-or-later" that I read about in the docs. But this isn't
accepted by hackage. The upload candidate page responds with

darcs-2.14.4/darcs.cabal:0:0: version with tags

and cabal check says

Warning: These warnings may cause trouble when distributing the package:
Warning: 'license: GPL-2.0' is not a known version of that license. The
known
versions are 2, 3. If this is not a mistake and you think it should be a
known
version then please file a ticket.
Warning: darcs.cabal:4:33: version with tags

Note we have

cabal-version: 1.24

in the cabal file, otherwise we could not support older ghc versions (we
currently support ghc-8.0 and later).

How can I fix this?