How to fix T5979?

[Herbert Valerio Riedel]

On 2014-05-10 at 18:30:40 +0200, Joachim Breitner wrote:

[...]

> now I also get SPJ’s output. I did not get it until I ran "git submodule
> update && make", and the reason might be that now, two versions of
> transformers are registered in the inplace data base
>
> $ ./inplace/bin/ghc-pkg list|grep transformers
>     transformers-0.3.0.0
>     transformers-0.4.0.0
> and after
> $ ./inplace/bin/ghc-pkg unregister transformers-0.3.0.0
> I get the original output.
>
> Reverting the test output for now.

very strange... where does transformers-0.3.0.0 come from? does the
build-tree contain a second transformers folder?