Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: acme-everything (user goal)
rejecting: acme-everything-2015.5.4.1, 2015.5.4, 2015.4.15.1 (global
constraint requires ==2015.4.15)
trying: acme-everything-2015.4.15
trying: AC-HalfInteger-1.2.1 (dependency of acme-everything-2015.4.15)
trying: base-4.8.1.0/installed-4f7... (dependency of AC-HalfInteger-1.2.1)
next goal: 4Blocks (dependency of acme-everything-2015.4.15)
rejecting: 4Blocks-0.2, 0.1 (conflict: base==4.8.1.0/installed-4f7..., 4Blocks
=> base>=2 && <=4)
Dependency tree exhaustively searched.