Add tox buildbot testing scenario

.buildbot/tox/Dockerfile

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+FROM ubuntu:bionic AS tox
+
+RUN apt-get update
+
+# Common apt packages
+RUN apt-get install -yq --no-install-suggests --no-install-recommends \
+    software-properties-common build-essential libcap-dev libssl-dev \
+    python-all-dev python-setuptools wget xvfb language-pack-en \
+    libffi-dev python3-dev python3-pip python3.8 python3.8-dev python3.8-venv \
+    python-msgpack python-pip python-qt4 python-six qtbase5-dev qt5-default \
+    tor
+
+RUN python3.8 -m pip install setuptools wheel
+RUN python3.8 -m pip install --upgrade pip tox virtualenv
+
+ENV LANG en_US.UTF-8
+ENV LANGUAGE en_US:en
+ENV LC_ALL en_US.UTF-8

.buildbot/tox/test.sh

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+#!/bin/sh
+
+tox