Add twine check to publish process (#6770)

Author: rpkilby

setup.py

@@ -56,6 +56,10 @@ def get_version(package):
         print("twine not installed.\nUse `pip install twine`.\nExiting.")
         sys.exit()
     os.system("python setup.py sdist bdist_wheel")
+    if os.system("twine check dist/*"):
+        print("twine check failed. Packages might be outdated.")
+        print("Try using `pip install -U twine wheel`.\nExiting.")
+        sys.exit()
     os.system("twine upload dist/*")
     print("You probably want to also tag the version now:")
     print("  git tag -a %s -m 'version %s'" % (version, version))