fix(.gitlab-ci.yml): review ssh key for github push

  - 'command -v ssh-agent >/dev/null || ( apt-get update -y && apt-get install openssh-client -y )'

  # run ssh-agent (inside the build environment)

  - eval $(ssh-agent -s)

  # give the right permissions, otherwise ssh-add will refuse to add files

  - chmod 400 "$SSH_PRIVATE_KEY"

  # add the SSH key stored in SSH_PRIVATE_KEY file type CI/CD variable to the agent store

  - ssh-add "$SSH_PRIVATE_KEY"

  # create the SSH directory and give it the right permissions

  - mkdir -p ~/.ssh

  - chmod 700 ~/.ssh

  # give the right permissions, otherwise ssh-add will refuse to add files

  - echo "$SSH_PRIVATE_KEY" > ~/.ssh/id_gitlab_rsa

  - chmod 400 ~/.ssh/id_gitlab_rsa

  # add the SSH key stored in SSH_PRIVATE_KEY file type CI/CD variable to the agent store

  - ssh-add ~/.ssh/id_gitlab_rsa

stages:

  - test-python-install