Add new --config flag to authentic2-ctl (fixes #5960)

--config expects the path to the config file, it --config is not used
the environment variable DJANGO_CONFIG_FILE is used instead.

authentic2-ctl

@@ -1,9 +1,27 @@
 #!/usr/bin/env python
-import os, sys
+import os
+import sys
 
 if __name__ == "__main__":
+    config_file = False
+
+    argv = sys.argv[1:]
+    for arg in list(argv):
+        if arg.startswith('--'):
+            if arg.startswith('--config='):
+                config_file = arg.split('=')[1]
+                argv.pop(0)
+            else:
+                print >>sys.stderr, 'ERR: Unsupported flag', arg
+                sys.exit(1)
+        else:
+            break
+
+    if config_file:
+        os.environ['DJANGO_CONFIG_FILE'] = config_file
+
     os.environ.setdefault("DJANGO_SETTINGS_MODULE", "authentic2.settings")
 
     from django.core.management import execute_from_command_line
 
-    execute_from_command_line(sys.argv)
+    execute_from_command_line(sys.argv[:1] + argv)