lint: flake8 4.0.1

Author: fanquake

ci/lint/04_install.sh

@@ -12,7 +12,7 @@ update-alternatives --install /usr/bin/clang-format      clang-format      "$(wh
 update-alternatives --install /usr/bin/clang-format-diff clang-format-diff "$(which clang-format-diff-9)" 100
 
 ${CI_RETRY_EXE} pip3 install codespell==2.1.0
-${CI_RETRY_EXE} pip3 install flake8==3.8.3
+${CI_RETRY_EXE} pip3 install flake8==4.0.1
 ${CI_RETRY_EXE} pip3 install mypy==0.910
 ${CI_RETRY_EXE} pip3 install pyzmq==22.3.0
 ${CI_RETRY_EXE} pip3 install vulture==2.3