Add Python as a pre-requisite

Make spaces consistent in Makefile

Author: stevepiercy

Makefile

@@ -62,7 +62,7 @@ docs/volto:
 	@echo "Documentation of volto initialized."
 
 .PHONY: deps
-deps: bin/python docs/volto docs/plone.restapi docs/plone.api ## Create Python virtual environment, install requirements, initialize or update the volto, plone.restapi, and plone.api submodules, and finally create symlinks to the source files.
+deps: bin/python docs/volto docs/plone.restapi docs/plone.api  ## Create Python virtual environment, install requirements, initialize or update the volto, plone.restapi, and plone.api submodules, and finally create symlinks to the source files.
 
 
 .PHONY: html

docs/contributing/setup-build.md

@@ -21,6 +21,15 @@ This document covers how to build the Plone Documentation and check it for quali
 Installation of Plone 6 Documentation includes pre-requisites and the repository itself.
 
 
+(setup-build-installation-python-label)=
+
+### Python
+
+Python 3.8 or later is required.
+A more recent Python is preferred.
+Use your system's package manager or [pyenv](https://github.com/pyenv/pyenv) to install an appropriate version of Python.
+
+
 (setup-build-installation-vale-label)=
 
 ### Vale