I had a look to the CI. Here is the meaning full error message.
E: Failed to fetch http://apt.postgresql.org/pub/repos/apt/dists/ **trusty-pgdg** /main/binary-i386/Packages
While building the environment, it try to install package from this repo.Trusty is a reference to an Ubuntu version of 2014, end of life 2019. Now postgresql is not delivering this package any more, we can see that here :
http://apt.postgresql.org/pub/repos/apt/dists/