otherwise, some wheel may not install.

- use python3 venv module to replace old bundled virtualenv module.
- upgrade docker build image and runtime image to debian buster based.
- bugfix: venv cache dir includes python version in dir name.

make wheel should use && to connect commands so that "ready" file is not
created when some command failed.

- use PYPI_MIRROR in make wheel and make dist.

default TZ set to CST-8 (Asia/Shanghai)

- "make loc" now run cloc on $(PYTHON_MODULES) instead of just the main pkg.
- minor, "make full-clean" don't care about .venv-* wheelhouse-*. Those
  files are in global cache dir.

wheelhouse/ dir;

- don't rebuild wheelhouse/ if ready file exists.
  use shell if to check this.

  makefile mtime based check won't work when git checkout file is newer
  than last build's ready file.

and wheelhouse to speed up build.

bootstrap and bootstrap-dev now don't check for library if requirements
file have not changed.

"make wheel" will be no-op if requirements file have not changed.

dropped usage of CI_BUILD=1 env variable, it is not used.

this is required for propery python3 unicode literal string support.

- W504 and W503 is just bad.
- E122, E129 programmer usually do the right thing himself.
  When this is not the case, these rules are not helpful.

upgraded default python-build-image version.

- allow set DOCKER_IMAGE_PREFIX and KUBECTL_CA_PATH via env variable
- bugfix: properly escape DOCKER_PASSWORD when running docker login
- bugfix: properly config cache for pip when running "make ci-build"
  it needs a dir at /.cache that the current user can write into, inside
  the "docker run" docker container.

make bootstrap-dev will call this when running unit test.

old version doesn't work on some python versions.

- no longer use install command to copy them at install time.
- this allow better handling of systemd service file.
  also allow user to run apt remove and purge.

user should update ./utils/build-deb and deb-scripts if systemd service
file is used.

also dropped support for upstart. upstart is irrelevant now.

- pep8 ignore W503 instead of W504.

notifempty    don't rotate if log file is empty
compress      compress rotated file
delaycompress compress on next rotation cycle

these allow author to build dist and upload dist to pypi.org

setup.py uses GPLv3+ by default, was GPLv2+

use compatible version (~=) for all dependencies there.

restrict some pkg to versions that does support python2.7, latest
version only support for python3.4+.

previously it was trying to call jenkins api, which I haven't used for
years. replaced it with an empty shell script with some comments.