Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: zeromq4-haskell (user goal)
rejecting: zeromq4-haskell-0.6.5, zeromq4-haskell-0.6.4,
zeromq4-haskell-0.6.3, zeromq4-haskell-0.6.2, zeromq4-haskell-0.6.1,
zeromq4-haskell-0.6, zeromq4-haskell-0.5.1, zeromq4-haskell-0.5,
zeromq4-haskell-0.4.1, zeromq4-haskell-0.4, zeromq4-haskell-0.3.2,
zeromq4-haskell-0.3.1 (constraint from user target requires ==0.3)
rejecting: zeromq4-haskell-0.3 (conflict: requires pkg-config package
libzmq>=4.0 && <5.0, not found in the pkg-config database)
rejecting: zeromq4-haskell-0.2, zeromq4-haskell-0.1 (constraint from user
target requires ==0.3)
Dependency tree exhaustively searched.