Resolving dependencies...
cabal: Could not resolve dependencies:
trying: hnormalise-0.5.0.0 (user goal)
trying: async-2.1.1.1 (dependency of stm-conduit-3.0.0)
next goal: zeromq4-haskell (dependency of hnormalise-0.5.0.0)
rejecting: zeromq4-haskell-0.6.7, zeromq4-haskell-0.6.6,
zeromq4-haskell-0.6.5, zeromq4-haskell-0.6.4 (conflict: requires pkg-config
package libzmq>=4.0 && <5.0, not found in the pkg-config database)
rejecting: 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, zeromq4-haskell-0.3,
zeromq4-haskell-0.2, zeromq4-haskell-0.1 (conflict: async==2.1.1.1,
zeromq4-haskell => async==2.0.*)
Backjump limit reached (currently 2000, change with --max-backjumps or try to
run with --reorder-goals).