Python setup issues

This could be an issue with incomplete or inaccurate contributing docs. tldr; `./gradlew check` fails on Debian after initial checkout.

The docs say that one should first run:

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

but even after running this pieces are missing. I'm still debugging exactly what's missing but the symptoms look like this:

> Task :sdks:python:test-suites:tox:py35:setupVirtualenv FAILED
The path python3.5 (from --python=python3.5) does not exist

> Task :sdks:python:test-suites:tox:py36:setupVirtualenv FAILED
[ant:fmpp] Traceback (most recent call last):
[ant:fmpp] File "/usr/lib/python3/dist-packages/virtualenv.py", line 25, in <module>
[ant:fmpp] import distutils.sysconfig
[ant:fmpp] ModuleNotFoundError: No module named 'distutils.sysconfig'

...

FAILURE: Build completed with 2 failures.

1: Task failed with an exception.
-----------

• What went wrong:
  Execution failed for task ':sdks:python:test-suites:tox:py35:setupVirtualenv'.
  > Process 'command 'virtualenv'' finished with non-zero exit value 3

Indeed there is no Python 3.5 on this system:

gnome-user-share python2.6
gnome-vfs-2.0 python2.7
gnupg python3
gnupg2 python3.6
gold-ld python3.7
goobuntu-config-tools python3.8

But nowhere in the setup docs do we say that Python 3.5 is required to build this.