Resolving dependencies... cabal: '/opt/ghc/7.10.2/bin/ghc' exited with an error: : cannot satisfy -package-id bifunctors-5.1-dcf71160f0d82119077797419062a5c0 (use -v for more information) Failed to install free-4.12.1 cabal: Error: some packages failed to install: cgrep-6.5.0 depends on free-4.12.1 which failed to install. either-4.4.1 depends on free-4.12.1 which failed to install. free-4.12.1 failed during the final install step. The exception was: ExitFailure 1