Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: Pugs (user goal)
rejecting: Pugs-6.2.13.20150815, 6.2.13.20130611, 6.2.13.20120717,
6.2.13.20120203, 6.2.13.20111008, 6.2.13.20110925, 6.2.13.20110519 (global
constraint requires ==6.2.13.16)
trying: Pugs-6.2.13.16
trying: base-4.8.1.0/installed-4f7... (dependency of Pugs-6.2.13.16)
next goal: parsec (dependency of Pugs-6.2.13.16)
rejecting: parsec-3.1.9, 3.1.8, 3.1.7, 3.1.6, 3.1.5, 3.1.4, 3.1.3, 3.1.2,
3.1.1, 3.1.0, 3.0.1, 3.0.0 (conflict: Pugs => parsec<3.0.0)
rejecting: parsec-2.1.0.1, 2.1.0.0, 2.0 (conflict:
base==4.8.1.0/installed-4f7..., parsec => base<4.8)
Dependency tree exhaustively searched.