Ubuntu 16.04.7 LTS: xenial-pgdg Release' does not have a Release file.

[robert rottermann]

Hi Colleagues

when I try to apt update my Ubuntu 16.04.7 LTS server, I get the error

W: The repository 'http://apt.postgresql.org/pub/repos/apt xenial-pgdg Release' 
does not have a Release file.
W: Failed to fetch 
http://apt.postgresql.org/pub/repos/apt/dists/xenial-pgdg/main/binary-amd64/Packages: 
404  Not Found [IP: 217.196.149.55 80]


what can I do to fix this?

thanks for your help

robert