Fix #1204 - Restore pytz depencency #845

Job	Run time
build-docker (internet.nl, docker/Dockerfile, app)	5m 16s
build-docker (unbound, docker/Dockerfile, unbound)	1m 10s
build-docker (linttest, docker/Dockerfile, linttest)	3m 48s
build-docker (test-runner, docker/test-runner.Dockerfile)	55s
build-docker (webserver, docker/webserver.Dockerfile)	1m 19s
build-docker (rabbitmq, docker/rabbitmq.Dockerfile)	1m 7s
build-docker (grafana, docker/grafana.Dockerfile)	1m 5s
build-docker (prometheus, docker/prometheus.Dockerfile)	51s
build-docker (cron, docker/cron.Dockerfile)	53s
integration-test	2m 54s
lint/check	44s
docs	1s
development-environment-test	2m 8s
test	2m 21s
	24m 32s

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