Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: acme-everything (user goal)
rejecting: acme-everything-2015.5.4.1, acme-everything-2015.5.4,
acme-everything-2015.4.15.1 (constraint from user target requires ==2015.4.15)
trying: acme-everything-2015.4.15
trying: base-4.9.0.0/installed-4.9... (dependency of AC-HalfInteger-1.2.1)
next goal: 4Blocks (dependency of acme-everything-2015.4.15)
rejecting: 4Blocks-0.2, 4Blocks-0.1 (conflict: base==4.9.0.0/installed-4.9...,
4Blocks => base>=2 && <=4)
Dependency tree exhaustively searched.