ci: add tox and gitlab-ci

.gitlab-ci.yml

+---
+default:
+  image: python:3.7
+
+include:
+  - project: "open-source/gitlab-ci-templates"
+    ref: "branch/default"
+    file:
+      - "templates/no-duplicated-ci-pipelines.yml"
+      - "templates/lint/black.yml"
+      - "templates/lint/check-manifest.yml"
+      - "templates/lint/flake8.yml"
+      - "templates/lint/mypy.yml"
+      - "templates/lint/safety.yml"
+      - "templates/lint/yamllint.yml"
+      - "templates/tests/py3.yml"
+      - "templates/create-release-on-heptapod.yml"
+      - "templates/upload-python-package-to-heptapod.yml"
+
+stages:
+  - lint
+  - tests
+  - build
+  - release
+  - publish

.hgignore

@@ -2,3 +2,5 @@
 (^|/)\.hg($|/)
 (^|/)\.hgtags($|/)
 ^log$
+.tox/
+.egg-info/

tox.ini

+[tox]
+envlist = py3,flake8,check-manifest,black
+
+[testenv]
+deps =
+  pytest
+  git+https://github.com/psycojoker/pytest-capture-deprecatedwarnings
+commands =
+  {envpython} -m pytest {posargs:test}
+
+[testenv:flake8]
+basepython = python3
+skip_install = true
+deps =
+  flake8 >= 3.6
+commands = {envpython} -m flake8 {toxinidir} {posargs}
+
+[testenv:check-manifest]
+skip_install = true
+deps =
+  check-manifest
+commands =
+  {envpython} -m check_manifest {toxinidir}
+
+[testenv:yamllint]
+skip_install = true
+deps = yamllint
+commands =
+  yamllint .
+
+[testenv:safety]
+deps =
+    safety
+commands =
+    safety check
+
+[testenv:mypy]
+deps =
+  mypy >= 0.761
+commands = mypy --ignore-missing-imports pybill
+
+[testenv:black]
+basepython = python3
+skip_install = true
+deps =
+  black >= 19.10b0
+commands = black --check .
+
+[testenv:black-run]
+basepython = python3
+skip_install = true
+deps =
+  black >= 19.10b0
+commands = black .
+
+[testenv:pypi-publish]
+basepython = python3
+skip_install = true
+whitelist_externals = rm
+deps =
+  twine
+passenv =
+  TWINE_USERNAME
+  TWINE_PASSWORD
+commands =
+  rm -rf build dist .egg .egg-info
+  python3 setup.py sdist bdist_wheel
+  twine check dist/*
+  twine upload --skip-existing dist/*
+
+[flake8]
+basepython = python3
+format = pylint
+ignore = W503, E203, E731, E231, E501
+max-line-length = 100
+exclude = test/data/*,.tox/*,doc/*
+
+[pytest]
+python_files = *test_*.py
+testpaths = test
+addopts = -r fEs