re: 404 repo libpq-dev

Hi all-
I resolved issue with 404 error. I had looked at docs on postgresql site
and they said add an extra repo for postgesql to ubuntu, so I did.
Then I came back later to postgresql site and found that the next
paragraph  under those instructions said oh ...btw, the default in
postgresql for ubuntu 18.04 is 10.x., and you dont need to add the extra
repo.

So I downgraded to 10 and removed the extra repo. It now let's me install
libpq-dev as it now matches version for libpq5 (10.x).

I hope I have 10 on there correctly now. I will find out soon enough.

Thnx- roboloki