Add tox initialization.

tests/test_stack_yaml.py

@@ -1,5 +1,4 @@
 import os
-import pytest
 
 
 def test_stack_functions(stack_data):

tox.ini

@@ -0,0 +1,30 @@
+[tox]
+minversion = 3.8.6
+envlist =
+    lint
+
+[testenv]
+basepython = python3.7
+passenv = *
+setenv =
+    PYTHONDONTWRITEBYTECODE=1
+commands_pre =
+    find {toxinidir} -type f -not -path '{toxinidir}/.tox/*' -path '*/__pycache__/*' -path '*/build/*' -name '*.py[c|o]' -delete
+whitelist_externals =
+    find
+    bash
+# Enabling sitepackages is needed if you need to avoid encountering exceptions
+# caused by missing selinux python bindinds in ansible modules like template.
+# Selinux python bindings are binary and they cannot be installed using pip
+# in virtualenvs. Details: https://github.com/ansible/molecule/issues/1724
+sitepackages = false
+
+[flake8]
+max-line-length = 90
+max-complexity = 10
+
+[testenv:lint]
+deps = flake8>=3.6.0,<4
+commands = flake8 tests
+skip_install = true
+usedevelop = false