Beam site says to install tox, but GitHub README does not

https://beam.apache.org/contribute/ says "Python, virtualenv, and tox installed for Python SDK development"

However, https://github.com/apache/beam says

If you'd like to build and install the whole project from the source distribution, you may need some additional tools installed in your system. In a Debian-based distribution:

sudo apt-get install \
openjdk-8-jdk \
python-setuptools \
python-pip \
virtualenv

Notice the second makes no mention of tox. Please sync up these instructions.