This package backports the Control.Monad.Except module from mtl (if using
mtl-2.2.0.1 or earlier), which reexports the ExceptT monad transformer and the
MonadError class.

This package should only be used if there is a need to use the
Control.Monad.Except module specifically. If you just want the mtl class
instances for ExceptT, use transformers-compat instead, since mtl-compat does
nothing but reexport the instances from that package.
