docs/make_a_release: Ensure uploaded distributions are signed

Author: jcfr

docs/make_a_release.rst

@@ -5,7 +5,7 @@ How to Make a Release
 A core developer should use the following steps to create a release of
 **cmake-python-distributions**.
 
-0. Configure `~/.pypirc` as described `here <http://peterdowns.com/posts/first-time-with-pypi.html>`_.
+0. Configure `~/.pypirc` as described `here <https://packaging.python.org/distributing/#uploading-your-project-to-pypi>`_.
 
 1. Make sure that all CI tests are passing: `AppVeyor <https://ci.appveyor.com/project/scikit-build/cmake-python-distributions-f3rbb>`_,
    `CircleCI <https://circleci.com/gh/scikit-build/cmake-python-distributions>`_
@@ -37,13 +37,13 @@ A core developer should use the following steps to create a release of
 
 4. Upload the packages to the testing PyPI instance::
 
-    twine upload -r pypitest dist/*
+    twine upload --sign -r pypitest dist/*
 
 5. Check the `PyPI testing package page <https://testpypi.python.org/pypi/cmake/>`_.
 
 6. Upload the packages to the PyPI instance::
 
-    twine upload dist/*
+    twine upload --sign dist/*
 
 7. Check the `PyPI package page <https://pypi.python.org/pypi/cmake/>`_.