Improve Installation Message on Ubuntu

[JulianBirch]

When I install something that uses postgresql-libpq and get the following message:

You need to install postgresql-server-dev-X.Y for building a
server-side extension or libpq-dev for building a client-side application.

It'd be nice to include some text pointing someone at apt-get to avoid confusion between installing OS packages and cabal packages.

[lpsmith]

Honestly, I'm not even sure where that message is coming from, it's not coming from postgresql-libpq or cabal. It has to be some trick Ubuntu is pulling when GHC/Cabal's build process is running CPP and trying to include the non-existent libpq headers.

So, I don't think it's really all that fixable, other than doing a apt-get install libpq-dev or the like. Though there should be some installation instructions included in the .cabal Description field.

[JulianBirch]

Oh well :(

[lpsmith]

Well, I'll definitely try to work on the installation instructions soon, which should help.

Since Hackage is a bit funky in the way that the description field is rendered, I'm thinking of just having the instructions as the README.md on github with a link in the description field. Which is not as good, but still a big step in the right direction...

[lpsmith]

Alternatively, if you track down how Ubuntu is generating that message, you might suggest this sort of improvement there...