Re: Look into Haskell packageSourceOverrides

[Chris Warburton]

Not really actionable.

For particular applications, e.g. panpipe, I think we're better off with
IOHK's haskell.nix approach, since that solves dependencies using Cabal,
which has two advantages:

 - We don't need to manually specify versions for dependencies, etc.
 - If the solution chosen by Cabal doesn't work, that's a problem with
   the package's version bounds, not with the way it's been packaged for
   Nix; the "correct" fix is to change those bounds.

For those cases where we are overriding the Nixpkgs haskellPackages set,
I don't think packageSourceOverrides would be enough. For example, some
packages get their test suite disabled, others get extra dependencies
added, etc. which seems to be more general than this function allows.