Forward environment to cron via crontab file

Dockerfile

@@ -6,9 +6,7 @@ RUN \
     apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 ADD files/main.py /main.py
+ADD files/entrypoint.sh /entrypoint.sh
+ADD files/crontab.tpl /crontab.tpl
 
-ADD files/crontab /etc/cron.d/assembly-cron
-RUN chmod 0644 /etc/cron.d/assembly-cron
-RUN crontab /etc/cron.d/assembly-cron
-
-CMD ["cron", "-f"]
+ENTRYPOINT ["/entrypoint.sh"]

files/entrypoint.sh

@@ -0,0 +1,14 @@
+#!/bin/bash
+
+# Create crontab with current environment variables
+(
+  printenv
+  echo
+  cat /crontab.tpl
+) > /etc/cron.d/assembly-cron
+
+# Install crontab
+crontab /etc/cron.d/assembly-cron
+
+# Run cron daemon
+exec cron -f

files/main.py

@@ -1,4 +1,5 @@
 #!/usr/bin/env python3
+# vim: sw=2:ts=2:noet
 # -*- coding: utf-8 -*-
 #
 ####  Assemble the Undead				#####
@@ -55,8 +56,8 @@ smtp_from			= os.getenv('SMTP_FROM')
 smtp_user			  = os.getenv('SMTP_USER')
 smtp_password		= os.getenv('SMTP_PASSWORD')
 mail_subject		= os.getenv('MAIL_SUBJECT')
-mail_header			= os.getenv('MAIL_HEADER')
-mail_footer			= os.getenv('MAIL_FOOTER')
+mail_header			= os.getenv('MAIL_HEADER').replace("\\n","\n")
+mail_footer			= os.getenv('MAIL_FOOTER').replace("\\n","\n")
 
 def main(args):