Add pre-commit config and linting

* pre-commit config with common hooks used in pytest
* Add "linting" tox-env
* Add "testing" extras

Author: nicoddemus

.pre-commit-config.yaml

@@ -0,0 +1,32 @@
+exclude: doc/en/example/py2py3/test_py2.py
+repos:
+-   repo: https://github.com/python/black
+    rev: 19.3b0
+    hooks:
+    -   id: black
+        args: [--safe, --quiet]
+-   repo: https://github.com/asottile/blacken-docs
+    rev: v1.0.0
+    hooks:
+    -   id: blacken-docs
+        additional_dependencies: [black==19.3b0]
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.2.3
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: fix-encoding-pragma
+    -   id: check-yaml
+-   repo: https://github.com/asottile/reorder_python_imports
+    rev: v1.4.0
+    hooks:
+    -   id: reorder-python-imports
+        args: ['--application-directories=execnet']
+-   repo: local
+    hooks:
+    -   id: rst
+        name: rst
+        entry: rst-lint --encoding utf-8
+        files: ^(CHANGELOG.rst|HOWTORELEASE.rst|README.rst)$
+        language: python
+        additional_dependencies: [pygments, restructuredtext_lint]

.travis.yml

@@ -16,6 +16,8 @@ jobs:
     - stage: baseline
       env: TOXENV=docs
       python: '3.6'
+    - env: TOXENV=linting
+      python: '3.6'
     - env: TOXENV=py27
       python: '2.7'
     - env: TOXENV=py37

setup.py

@@ -34,6 +34,11 @@ def main():
         packages=['execnet', 'execnet.script'],
         python_requires=">=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*",
         install_requires=['apipkg>=1.4'],
+        extras_require={
+            "testing": [
+                "pre-commit",
+            ],
+        },
         setup_requires=['setuptools_scm'],
     )
 

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist=py27,py34,py35,py36,py37,pypy,pypy3
+envlist=py27,py37,docs,linting
 
 [testenv]
 deps=
@@ -18,6 +18,12 @@ deps =
 commands =
     sphinx-build -W -b html . _build
 
+[testenv:linting]
+skip_install = True
+basepython = python3
+deps = pre-commit>=1.11.0
+commands = pre-commit run --all-files --show-diff-on-failure
+
 [pytest]
 timeout = 20
 addopts = -ra