get config filename from env variable RADICALE_CONFIG

radicale/config.py

@@ -74,6 +74,8 @@ for section, values in INITIAL_CONFIG.items():
 
 _CONFIG_PARSER.read("/etc/radicale/config")
 _CONFIG_PARSER.read(os.path.expanduser("~/.config/radicale/config"))
+if os.environ.get('RADICALE_CONFIG', None):
+    _CONFIG_PARSER.read(os.environ['RADICALE_CONFIG'])
 
 # Wrap config module into ConfigParser instance
 sys.modules[__name__] = _CONFIG_PARSER