make build is using charmcraft python pkg in tox and failed for missing dependency

Currently charm build is triggered via:

make build -> tox -e build -> charmcraft python pkg in venv

The charmcraft python pkg deps on python3-apt, and then python3-distutils-extra,

build will fail for missing `DistUtilsExtra` since it only has deb pkg but no python pkg:

```
ERROR: Command errored out with exit status 1:
   command: /home/guoqiao/charms/charm-cloudstats/.tox/build/bin/python -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-v9pscss6/python-apt_6a62d0f42e9b439098faee7649c06c59/setup.py'"'"'; __file__='"'"'/tmp/pip-install-v9pscss6/python-apt_6a62d0f42e9b439098faee7649c06c59/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' egg_info --egg-base /tmp/pip-pip-egg-info-d1tcxsmt
       cwd: /tmp/pip-install-v9pscss6/python-apt_6a62d0f42e9b439098faee7649c06c59/
  Complete output (5 lines):
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
    File "/tmp/pip-install-v9pscss6/python-apt_6a62d0f42e9b439098faee7649c06c59/setup.py", line 6, in <module>
      from DistUtilsExtra.command import *
  ModuleNotFoundError: No module named 'DistUtilsExtra'
```

We may need to switch to snap to avoid this issue.