message: ci: Install fixed version of clang-format for linters
diff: export LC_ALL=C
  +travis_retry sudo apt update && sudo apt install -y clang-format-9
  +sudo update-alternatives --install /usr/bin/clang-format clang-format $(which clang-format-9 ) 100
  +sudo update-alternatives --install /usr/bin/clang-format-diff clang-format-diff $(which clang-format-diff-9) 100
  +
  travis_retry pip3 install codespell==1.17.1
  travis_retry pip3 install flake8==3.8.3
  travis_retry pip3 install yq
  