EXPKEYSIG error during installation
When running the first cell of the Google Colab notebook provided in the installation instructions wiki, there is an error about an invalid signature.
Executing: /tmp/apt-key-gpghome.DHTXI632Su/gpg.1.sh --keyserver keyserver.ubuntu.com --recv-key 612DEFB798507F25
gpg: key 612DEFB798507F25: public key "Tiago de Paula Peixoto <tiago@skewed.de>" imported
gpg: Total number processed: 1
gpg: imported: 1
Get:1 https://cloud.r-project.org/bin/linux/ubuntu bionic-cran40/ InRelease [3,626 B]
Hit:2 http://ppa.launchpad.net/c2d4u.team/c2d4u4.0+/ubuntu bionic InRelease
Hit:3 http://archive.ubuntu.com/ubuntu bionic InRelease
Get:4 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Get:5 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:6 http://downloads.skewed.de/apt bionic InRelease [7,540 B]
Ign:7 https://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu1804/x86_64 InRelease
Get:8 https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64 InRelease [1,581 B]
Hit:9 http://ppa.launchpad.net/cran/libgit2/ubuntu bionic InRelease
Hit:10 https://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu1804/x86_64 Release
Err:6 http://downloads.skewed.de/apt bionic InRelease
The following signatures were invalid: EXPKEYSIG 7A80C8ED4FCCBE09 Tiago de Paula Peixoto <tiago@skewed.de>
Get:11 https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64 Packages [985 kB]
Hit:12 http://ppa.launchpad.net/deadsnakes/ppa/ubuntu bionic InRelease
Get:13 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [83.3 kB]
Hit:14 http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu bionic InRelease
Get:16 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 Packages [1,554 kB]
Get:17 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [3,467 kB]
Get:18 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages [3,035 kB]
Get:19 http://archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [2,332 kB]
Reading package lists... Done
W: GPG error: http://downloads.skewed.de/apt bionic InRelease: The following signatures were invalid: EXPKEYSIG 7A80C8ED4FCCBE09 Tiago de Paula Peixoto <tiago@skewed.de>
E: The repository 'http://downloads.skewed.de/apt bionic InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package python3-graph-tool