Add a way to run tests in PostgreSQL in Docker (#3699)

docker/Dockerfile-pgtests

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+# Use the Sytest image that comes with a lot of the build dependencies
+# pre-installed
+FROM matrixdotorg/sytest:latest
+
+# The Sytest image doesn't come with python, so install that
+RUN apt-get -qq install -y python python-dev python-pip
+
+# We need tox to run the tests in run_pg_tests.sh
+RUN pip install tox
+
+ADD run_pg_tests.sh /pg_tests.sh
+ENTRYPOINT /pg_tests.sh

docker/run_pg_tests.sh

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+#!/bin/bash
+
+# This script runs the PostgreSQL tests inside a Docker container. It expects
+# the relevant source files to be mounted into /src (done automatically by the
+# caller script). It will set up the database, run it, and then use the tox
+# configuration to run the tests.
+
+set -e
+
+# Set PGUSER so Synapse's tests know what user to connect to the database with
+export PGUSER=postgres
+
+# Initialise & start the database
+su -c '/usr/lib/postgresql/9.6/bin/initdb -D /var/lib/postgresql/data -E "UTF-8" --lc-collate="en_US.UTF-8" --lc-ctype="en_US.UTF-8" --username=postgres' postgres
+su -c '/usr/lib/postgresql/9.6/bin/pg_ctl -w -D /var/lib/postgresql/data start' postgres
+
+# Run the tests
+cd /src
+export TRIAL_FLAGS="-j 4"
+tox --workdir=/tmp -e py27-postgres