Add a docker file

.gitignore

@@ -7,3 +7,4 @@ sygnal.pid
 sygnal.db
 /_trial_temp*
 /.idea
+*.egg-info

MANIFEST.in

@@ -0,0 +1,9 @@
+include *.md
+include *.rst
+include sygnal.yaml.sample
+include LICENSE
+include VERSION
+recursive-include tests *.py
+
+prune .buildkite
+prune docker

docker/Dockerfile

@@ -0,0 +1,39 @@
+# Dockerfile to build the matrixdotorg/sygnal docker images.
+#
+# To build the image, run `docker build` command from the root of the
+# sygnal repository:
+#
+#    docker build -f docker/Dockerfile .
+#
+
+###
+### Stage 0: builder
+###
+FROM python:3.7-slim as builder
+
+# build things which have slow build steps, before we copy sygnal, so that
+# the layer can be cached.
+#
+# (we really just care about caching a wheel here, as the "pip install" below
+# will install them again.)
+
+RUN pip install --prefix="/install" --no-warn-script-location cryptography
+
+# now install sygnal and all of the python deps to /install.
+
+COPY sygnal /sygnal/sygnal/
+COPY MANIFEST.in README.rst VERSION setup.py /sygnal/
+
+RUN pip install --prefix="/install" --no-warn-script-location /sygnal
+
+###
+### Stage 1: runtime
+###
+
+FROM python:3.7-slim
+
+COPY --from=builder /install /usr/local
+
+EXPOSE 5000/tcp
+
+ENTRYPOINT ["python", "-m", "sygnal.sygnal"]