install python3-is-python

.github/workflows/docker-coq.yml

@@ -42,7 +42,7 @@ jobs:
           etc/ci/describe-system-config.sh
     - name: remove autogenerated
       run: etc/ci/remove_autogenerated.sh
-    - name: install gcc
+    - name: install dependencies
       uses: coq-community/docker-coq-action@v1
       with:
         coq_version: ${{ matrix.env.DOCKER_COQ_VERSION }}
@@ -54,6 +54,10 @@ jobs:
            #sudo apt-get install g++-7 libssl-dev -y --allow-unauthenticated
            #sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 60 --slave /usr/bin/g++ g++ /usr/bin/g++-7
            #endGroup
+           startGroup 'install dependencies'
+           sudo apt-get -o Acquire::Retries=30 update -q
+           sudo apt-get -o Acquire::Retries=30 install python3-is-python -y --allow-unauthenticated
+           endGroup
     - name: some-early util
       uses: coq-community/docker-coq-action@v1
       with: