I'm running Linux Mint 19 Tara, and trying to follow the instructions here with the goal of installing pgAdmin4 as a desktop app. There seems to be a problem involving the authentication of the repository.
The apt-key step seems to work, as I observe
PostgreSQL Debian Repository in the apt-key list.
I don't have a
deb command (I imagine this is a Mint vs Ubuntu difference?), so I used
add-apt-repository http://apt.postgresql.org/pub/repos/apt/ tara-pgdg main
instead, after which I observe
deb http://apt.postgresql.org/pub/repos/apt/ bionic main
At this point running either
apt-get upgrade or
apt-get update shows an error
The repository 'http://apt.postgresql.org/pub/repos/apt bionic Release' does not have a Release file.
How can I proceed? It seems unlikely that there really isn't a release file; I can see what looks like an authentication list at https://apt.postgresql.org/pub/repos/apt/dists/bionic-pgdg/. Do I have a path wrong or something?