Resolving dependencies... cabal: Could not resolve dependencies: next goal: base91 (user goal) rejecting: base91-2.1.0, 2.0.0, 1.1.0, 1.0.1 (global constraint requires ==1.0.0) trying: base91-1.0.0 next goal: base (dependency of base91-1.0.0) rejecting: base-4.8.1.0/installed-4f7... (conflict: base91 => base<0) rejecting: base-4.8.1.0, 4.8.0.0, 4.7.0.2, 4.7.0.1, 4.7.0.0, 4.6.0.1, 4.6.0.0, 4.5.1.0, 4.5.0.0, 4.4.1.0, 4.4.0.0, 4.3.1.0, 4.3.0.0, 4.2.0.2, 4.2.0.1, 4.2.0.0, 4.1.0.0, 4.0.0.0, 3.0.3.2, 3.0.3.1 (global constraint requires installed instance) Dependency tree exhaustively searched.