Make several changes in the release and CI setup. (#509)

* Make several changes in the release and CI setup.

- Remove .travis/ directory completely.
- Update deploy.py script to tag with major.minor version
  and remove the v in the tag which it didn't before.
- Fix the CircleCI cron setup.

* Update config.yml

* Use buildkit if possible.

* Use machine executor which supports buildkit.

* Remove setup docker step

* Use newer image.

* Use buildkit syntax for caching pip dependencies.

This should significantly speed up the build process by not having
to build python wheels multiple times.

* Use plain output from buildkit

* Make deploy script work with Python 2.7

Also cache python deps across builds.

* Fix more python3 things

* Install dependency in python3

postorius/Dockerfile

@@ -1,7 +1,6 @@
+# syntax = docker/dockerfile:1.3
 FROM alpine:3.12
 
-MAINTAINER Abhilash Raj
-
 # Add needed files for uwsgi server + settings for django
 COPY mailman-web /opt/mailman-web
 # Add startup script to container
@@ -10,7 +9,8 @@ COPY docker-entrypoint.sh /usr/local/bin/
 # Install packages and dependencies for postorius and hyperkitty Add user for
 # executing apps, change ownership for uwsgi+django files and set execution
 # rights for management script
-RUN set -ex \
+RUN --mount=type=cache,target=/root/.cache \
+    set -ex \
 	&& apk add --no-cache --virtual .build-deps gcc libc-dev linux-headers \
 		postgresql-dev mariadb-dev python3-dev libffi-dev openldap-dev cargo rust \
 	&& apk add --no-cache --virtual .mailman-rundeps bash sassc \

postorius/Dockerfile.dev

@@ -1,7 +1,6 @@
+# syntax = docker/dockerfile:1.3
 FROM alpine:3.12
 
-MAINTAINER Abhilash Raj
-
 # Add needed files for uwsgi server + settings for django
 COPY mailman-web /opt/mailman-web
 # Add startup script to container
@@ -14,7 +13,8 @@ ARG CLIENT_REF
 # Install packages and dependencies for postorius and hyperkitty Add user for
 # executing apps, change ownership for uwsgi+django files and set execution
 # rights for management script
-RUN set -ex \
+RUN --mount=type=cache,target=/root/.cache \
+    set -ex \
 	&& apk add --no-cache --virtual .build-deps gcc libc-dev linux-headers \
 		postgresql-dev mariadb-dev python3-dev libffi-dev git cargo rust \
 	&& apk add --no-cache --virtual .mailman-rundeps bash sassc \