Use intersphinx references

Author: dukecat0

README.rst

@@ -6,8 +6,8 @@ http://packaging.python.org
 The "Python Packaging User Guide" (PyPUG) aims to be the authoritative resource on
 how to package and install distributions in Python using current tools.
 
-To follow the development of Python packaging, see the `Python
-Packaging Authority <https://www.pypa.io/en/latest/>`_.
+To follow the development of Python packaging, see the :doc:`Python
+Packaging Authority <pypa:index>`.
 
 Code of Conduct
 ---------------

source/contribute.rst

@@ -124,19 +124,16 @@ Though not required to contribute, it may be useful to build this guide locally
 in order to test your changes. In order to build this guide locally, you'll
 need:
 
-1. `Nox <https://nox.thea.codes/en/latest/>`_. You can install or upgrade
+1. :doc:`Nox <nox:index>`. You can install or upgrade
    nox using ``pip``:
 
    .. code-block:: bash
 
       python -m pip install --user nox
 
 2. Python 3.6. Our build scripts are designed to work with Python 3.6 only.
-   See the `Hitchhiker's Guide to Python installation instructions`_ to install
-   Python 3.6 on your operating system.
-
-.. _Hitchhiker's Guide to Python installation instructions:
-    https://docs.python-guide.org/starting/installation/
+   See the :doc:`Hitchhiker's Guide to Python installation instructions <python-guide:starting/installation>`
+   to install Python 3.6 on your operating system.
 
 To build the guide, run the following bash command in the source folder:
 

source/discussions/deploying-python-applications.rst

@@ -73,7 +73,7 @@ directory, independent of any other Python installation on the computer.
 
 A big advantage of Pynsist is that the Windows packages can be built on Linux.
 There are several examples for different kinds of programs (console, GUI) in
-the `documentation <https://pynsist.readthedocs.io/en/latest/>`__. The tool is released
+the `documentation <pynsist:index>`. The tool is released
 under the MIT-licence.
 
 Application bundles