I observed repeated and frequent (but not systematic) errors today with the following timeout when adding a repository:
Adding APT Sources
$ sudo -E apt-add-repository -y "ppa:ubuntu-toolchain-r/test"
gpg: keyring `/tmp/tmpogcdm68q/secring.gpg' created
gpg: keyring `/tmp/tmpogcdm68q/pubring.gpg' created
gpg: requesting key BA9EF27F from hkp server keyserver.ubuntu.com
Error: retrieving gpg key timed out.
gpg: keyserver timed out
gpg: keyserver receive failed: keyserver error
The command "sudo -E apt-add-repository -y "ppa:ubuntu-toolchain-r/test"" failed and exited with 1 during .
Your build has been stopped.