Update Docs with Python Setup Guide (#4187)

Author: michaelawyu

packages/google-cloud-core/README.rst

@@ -18,6 +18,10 @@ Quick Start
 
     $ pip install --upgrade google-cloud-core
 
+Fore more information on setting up your Python development environment, such as installing ``pip`` and on your system, please refer to `Python Development Environment Setup Guide`_ for Google Cloud Platform.
+
+.. _Python Development Environment Setup Guide: https://cloud.google.com/python/setup
+
 .. |pypi| image:: https://img.shields.io/pypi/v/google-cloud-core.svg
    :target: https://pypi.org/project/google-cloud-core/
 .. |versions| image:: https://img.shields.io/pypi/pyversions/google-cloud-core.svg