Installation of PostgreSQL-11: Depends: libllvm6.0 (>= 1:6.0~svn298832-1~) but it is not installable

Question

I've added the official repository to my sources.list,

deb http://apt.postgresql.org/pub/repos/apt/ cosmic-pgdg main 11

When I try to install PostgreSQL-11 on Ubuntu Cosmic (18.10), I get the following error

$ apt-get install postgresql-11
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 postgresql-11 : Depends: libllvm6.0 (>= 1:6.0~svn298832-1~) but it is not installable
E: Unable to correct problems, you have held broken packages.

How do I go about resolving this error?

Answer 1

This error is because the Official PostgreSQL PPA for Cosmic is currently building against libllvm6.0. That's an import from Debian Sid, currently Ubuntu is building against the newer libllvm7.0. To get access to this package you'll have to add the universe to your sources.list.

sudo add-apt-repository "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc) universe"