bug#23961: guix import hackage gtk3 fails

[Danny Milosavljevic]

$ guix import hackage gtk3
;;; note: source file /x/home/dannym/src/guix/gnu/packages/haskell.scm
;;;       newer than compiled /x/home/dannym/src/guix/gnu/packages/haskell.go
Syntax error: unexpected token : custom-setup (at line 131, column 0)
Syntax error: unexpected end of input
guix import: error: failed to download cabal file for package 'gtk3'