Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: GPipe (user goal)
rejecting: GPipe-2.1.8, GPipe-2.1.7, GPipe-2.1.6, GPipe-2.1.5, GPipe-1.4.1,
GPipe-2.1.4, GPipe-2.1.3, GPipe-2.1.2, GPipe-2.1.1, GPipe-2.1, GPipe-2.0.2,
GPipe-2.0.1, GPipe-2.0, GPipe-1.4, GPipe-1.3.2 (constraint from user target
requires ==1.3.1)
trying: GPipe-1.3.1
trying: base-4.9.0.0/installed-4.9... (dependency of GPipe-1.3.1)
next goal: Boolean (dependency of GPipe-1.3.1)
rejecting: Boolean-0.2.3, Boolean-0.2.2, Boolean-0.2.1, Boolean-0.2,
Boolean-0.1.2, Boolean-0.1.1, Boolean-0.1.0 (conflict: GPipe =>
Boolean==0.0.1)
rejecting: Boolean-0.0.1 (conflict: base==4.9.0.0/installed-4.9..., Boolean =>
base<4.8)
rejecting: Boolean-0.0.0 (conflict: GPipe => Boolean==0.0.1)
Dependency tree exhaustively searched.