Resolving dependencies...
cabal: Could not resolve dependencies:
next goal: operational-extra (user goal)
rejecting: operational-extra-0.4, operational-extra-0.3 (constraint from user
target requires ==0.2)
trying: operational-extra-0.2
next goal: transformers (dependency of operational-extra-0.2)
rejecting: transformers-0.5.2.0/installed-0.5..., transformers-0.5.2.0,
transformers-0.5.1.0, transformers-0.5.0.1, transformers-0.5.0.0,
transformers-0.4.3.0, transformers-0.4.2.0, transformers-0.4.1.0,
transformers-0.3.0.0, transformers-0.2.2.1, transformers-0.2.1.0,
transformers-0.2.0.0, transformers-0.1.4.0, transformers-0.1.3.0,
transformers-0.1.1.0, transformers-0.1.0.1, transformers-0.0.1.0,
transformers-0.0.0.0, transformers-0.5.0.2, transformers-0.4.0.0,
transformers-0.2.2.0, transformers-0.1.0.0 (conflict: operational-extra =>
transformers>=4.0)
Dependency tree exhaustively searched.