Emacs hangs with "Haskell Process Suggest Add Package"

If I enable this feature everything works fine - the process sees when there is a hidden package used, asks me if I want to include it into the `.cabal` file, includes it in the right places.

But once I get to the point where it asks me if I want to import it into the ghci session emacs hangs until I kill the GHC process from my system with my OS-process manager.

Reproduce the issue by enabling “Haskell Process Suggest Add Package” and reaching the prompt to import the package into the ghci session. Start by tracing the GHC process interaction at that prompt; done means Emacs remains responsive and the package is either imported or the prompt completes without requiring the GHC process to be killed.

Written by the indexing model from the issue text.