Hi Tiago,
I am not sure if this issue is sourced from graph-tool. When I try to download the public key, I get this error:
echo "deb http://downloads.skewed.de/apt bionic main" >> /etc/apt/sources.list
apt-key adv --keyserver keys.openpgp.org --recv-key 612DEFB798507F25
Error:
Executing: /tmp/apt-key-gpghome.wVeQRbY1M1/gpg.1.sh --keyserver keys.openpgp.org --recv-key 612DEFB798507F25
gpg: keyserver receive failed: General error
I did check all distributions as well.
Thank you