hackage-doc-tarball job failures

This job has been failing in nightly runs since 24 November

• https://gitlab.haskell.org/ghc/ghc/-/jobs/1242112
• https://gitlab.haskell.org/ghc/ghc/-/jobs/1243166
• https://gitlab.haskell.org/ghc/ghc/-/jobs/1243513
• https://gitlab.haskell.org/ghc/ghc/-/jobs/1244646
• https://gitlab.haskell.org/ghc/ghc/-/jobs/1245005
• https://gitlab.haskell.org/ghc/ghc/-/jobs/1245186
• https://gitlab.haskell.org/ghc/ghc/-/jobs/1245273

Last ~30 lines:

No cabal.project file or cabal file matching the default glob './*.cabal' was found.
Please create a package description file <pkgname>.cabal or a cabal.project file referencing the packages you want to build.
base
Processing base...
Preparing package base...
ghc-prim
Processing ghc-prim...
Preparing package ghc-prim...
Building _build/stage1/libraries/ghc-prim/build/GHC/PrimopWrappers.hs for libraries/ghc-prim/GHC/PrimopWrappers.hs...
integer-gmp
Processing integer-gmp...
Preparing package integer-gmp...
ghc-bignum
Processing ghc-bignum...
Preparing package ghc-bignum...
template-haskell
Processing template-haskell...
Preparing package template-haskell...
Traceback (most recent call last):
  File "./upload_ghc_libs.py", line 231, in <module>
    main()
  File "./upload_ghc_libs.py", line 212, in main
    pkg_meta = prepare_pkg(args.bindist, pkg)
  File "./upload_ghc_libs.py", line 178, in prepare_pkg
    p1 = prepare_sdist(pkg)
  File "./upload_ghc_libs.py", line 122, in prepare_sdist
    run(['cabal', 'sdist'], cwd=pkg.path, check=True)
  File "/usr/lib/python3.7/subprocess.py", line 487, in run
    output=stdout, stderr=stderr)
subprocess.CalledProcessError: Command '['cabal', 'sdist']' returned non-zero exit status 1.