Add tox build-check command

Author: grantjenks

tox.ini

@@ -26,3 +26,14 @@ testpaths=docs src/sortedcontainers tests
 [testenv:pylint]
 deps=pylint<2.6
 commands=pylint src/sortedcontainers
+
+[testenv:build-check]
+description=Builds source and binary packages and uses twine check to validate
+skip_install=True
+changedir={envtmpdir}
+deps=
+    pep517
+    twine
+commands=
+    python -m pep517.build -b -s {toxinidir} -o {envtmpdir}/dist
+    twine check {envtmpdir}/dist/*