Update azure-pipelines.yml for Azure Pipelines (#331)

* Update azure-pipelines.yml for Azure Pipelines

* Add Python build scripts.

* Run scripts with Python 3.

* Add strategy for both variants.

* Fix variables for jobs and use the right variant to build.

* Fix build and test script.

build.py

@@ -0,0 +1,79 @@
+#/usr/bin/env python3
+
+# This is the build script to build container images for Mailman.
+import sys
+import subprocess
+from pathlib import Path
+
+
+STABLE_DOCKERFILES = {
+    'core-stable': Path('core/Dockerfile'),
+    'web-stable': Path('web/Dockerfile'),
+    'postorius-stable': Path('postorius/Dockerfile'),
+}
+
+ROLLING_DOCKERFILES = {
+    'core-rolling': Path('core/Dockerfile.dev'),
+    'web-rolling': Path('web/Dockerfile.dev'),
+    'postorius-rolling': Path('postorius/Dockerfile.dev'),
+}
+
+VARIANTS = {
+    'stable': STABLE_DOCKERFILES,
+    'rolling': ROLLING_DOCKERFILES,
+}
+
+def run_command(args):
+    print(' '.join(args))
+    subprocess.run(
+        args,
+        stdout=sys.stdout,
+        stderr=sys.stderr,
+        check=True)
+
+
+def docker_build(dockerfile, tag, args=None, labels=None):
+    cmd = [
+        'docker', 'build',
+        '-t', tag,
+        '-f', str(dockerfile),
+        str(dockerfile.parent)
+    ]
+
+    if args:
+        for arg in args:
+            cmd.append('--build-arg')
+            cmd.append(arg)
+
+    if labels:
+        for label in labels:
+            cmd.append('--label')
+            cmd.append(label)
+
+    return run_command(cmd)
+
+
+def docker_tag(from_tag, to_tag):
+    cmd = [
+        'docker', 'tag',
+        from_tag, to_tag,
+    ]
+
+    return run_command(cmd)
+
+def usage():
+    print('usage: python build.py (stable|rolling)')
+
+
+if __name__ == '__main__':
+    if len(sys.argv) < 2:
+        usage()
+        sys.exit(1)
+
+    variant = sys.argv[1]
+    if variant not in VARIANTS:
+        usage()
+        sys.exit(1)
+
+    for name, path in VARIANTS[variant].items():
+        docker_build(dockerfile=path, tag=name)