[Haskell-cafe] conduit: Finalize field in PipeM

[Paolo Capriotti]

Hi,
I'm trying to write a function to convert a conduit to a Pipe (from
pipes-core), and I'm having trouble understanding why the `Finalize`
field in a `PipeM` constructor returns `r`. This makes it impossible
to create it from the corresponding `M` constructor in pipes-core,
since `M` includes an exception handler which is not guaranteed to run
fully, hence may not provide a return value. `HaveOutput` presents a
similar problem.