Use attribute access for args object

src/xfel_calibrate/nb_args.py

@@ -414,7 +414,8 @@ def parse_argv_and_load_nb(argv) -> Tuple[Dict, NBDetails]:
     not_reproducible_args = sorted(
         ('--' + x.replace('_', '-')
          for x in ['skip_env_freeze']
-         if args[x]))
+         if getattr(args, x))
+    )
 
     # If any of these arguments are set, present a warning.
     if not_reproducible_args: