Hi, It looks some urls and installation instructions have changed recently? I had a gitlab-ci that started failing: E: The repository 'http://downloads.skewed.de/apt/buster buster Release' does not have a Release file. I tried following the new instructions to update the tests, and while apt-get is not complaining anymore and the installation appears to be successful, when the tests run it is not able to find graph_tool. Here is a MWE that’s failing: (I replaced my usual pytest with a simple attempt to import the library to illustrate) (Note I’m using add-apt-repository. Previously I was using add-apt-repository -s but it seems like having the deb-src was breaking things) test: image: python:3.6-slim stage: test before_script: - apt-get update - apt-get install -y gnupg2 software-properties-common - apt-key adv --keyserver keys.openpgp.org --recv-key 612DEFB798507F25 - add-apt-repository "deb http://downloads.skewed.de/apt buster main" - apt-get update - apt-get install -y gcc python3-dev python3-pip - apt-get install -y python3-graph-tool # - pip3 install -r requirements.txt - pip3 freeze - python3 -c 'from graph_tool.all import *' Here is a snippet from the output. I didn’t see any error during installation (tried this both on gitlab and locally with gitlab-runner) $ apt-get install -y python3-graph-tool Reading package lists... Building dependency tree... Reading state information... The following additional packages will be installed: adwaita-icon-theme at-spi2-core blt dbus-user-session dconf-gsettings-backend dconf-service fontconfig fontconfig-config ... Need to get 115 MB of archives. After this operation, 575 MB of additional disk space will be used. ... Unpacking python3-graph-tool (2.31) ... Setting up libxdot4 (2.40.1-6) ... Setting up javascript-common (11) ... ... $ pip3 freeze $ python3 -c 'from graph_tool.all import *' Traceback (most recent call last): File "<string>", line 1, in <module> ModuleNotFoundError: No module named 'graph_tool' Running after script... ERROR: Job failed: exit code 1 FATAL: exit code 1