Add publish env to tox

Author: dmtucker

tox.ini

@@ -7,14 +7,15 @@ envlist =
     py36-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.50, 0.5x, 0.60, 0.6x, 0.70, 0.7x}
     py37-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.50, 0.5x, 0.60, 0.6x, 0.70, 0.7x}
     py38-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.71, 0.7x}
+    publish
     static
 
 [gh-actions]
 python =
     3.5: py35-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.50, 0.5x, 0.60, 0.6x, 0.70, 0.7x}
     3.6: py36-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.50, 0.5x, 0.60, 0.6x, 0.70, 0.7x}
     3.7: py37-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.50, 0.5x, 0.60, 0.6x, 0.70, 0.7x}
-    3.8: py38-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.71, 0.7x}, static
+    3.8: py38-pytest{3.5, 3.x, 4.0, 4.x, 5.0, 5.x}-mypy{0.71, 0.7x}, publish, static
 
 [testenv]
 deps =
@@ -88,6 +89,15 @@ deps =
     pytest-randomly ~= 2.1.1
 commands = py.test -p no:mypy --cov pytest_mypy --cov-fail-under 100 --cov-report term-missing {posargs:-n auto} tests
 
+[testenv:publish]
+passenv = TWINE_*
+deps =
+    pep517 ~= 0.8.0
+    twine ~= 3.2.0
+commands =
+    {envpython} -m pep517.build --out-dir {distdir} .
+    twine {posargs:check} {distdir}/*
+
 [testenv:static]
 deps =
     bandit ~= 1.6.2