On core-updates, GHC 7.10.2 fails to build, so there are currently no
Haskell packages for core-updates:

https://hydra.gnu.org/build/2414139

It looks like the libtinfo substitutions have stopped working:

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Installing library in
/tmp/guix-build-ghc-7.10.2.drv-0/ghc-7.10.2/ghc-bin/usr/lib/ghc-7.8.4/haskell2010-1.1.2.0
"/tmp/guix-build-ghc-7.10.2.drv-0/ghc-7.10.2/ghc-bin/usr/lib/ghc-7.8.4/bin/ghc-pkg" --force --global-package-db "/tmp/guix-build-ghc-7.10.2.drv-0/ghc-7.10.2/ghc-bin/usr/lib/ghc-7.8.4/package.conf.d" update rts/dist/package.conf.install
/tmp/guix-build-ghc-7.10.2.drv-0/ghc-7.10.2/ghc-bin/usr/lib/ghc-7.8.4/bin/ghc-pkg: error while loading shared libraries: libtinfo.so.5: cannot open shared object file: No such file or directory
make[1]: *** [ghc.mk:908: install_packages] Error 127
make: *** [Makefile:24: install] Error 2
phase `install-bin' failed after 9.3 seconds
builder for `/gnu/store/6nvmpr7z6rgg7px9m0z72k65ramd0w7k-ghc-7.10.2.drv' failed with exit code 1
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Will some Haskeller take a look?