Use string.Formatter.parse to get variables from path template

src/xfel_calibrate/calibrate.py

@@ -9,6 +9,7 @@ import os
 import pprint
 import re
 import stat
+import string
 import sys
 import textwrap
 import warnings
@@ -402,10 +403,8 @@ def make_extended_parser() -> argparse.ArgumentParser:
         #  Pulls out the variables in the templated path string, so that they
         #  can be added to the argument parser
         user_notebook_variables = [
-            k.value.id
-            for k
-            in ast.walk(ast.parse(f"f'{user_notebook_path}'"))
-            if isinstance(k, ast.FormattedValue)
+            name for (_, name, _, _) in string.Formatter().parse(user_notebook_path)
+            if name is not None
         ]
 
         user_notebook_parser = argparse.ArgumentParser()
@@ -417,7 +416,7 @@ def make_extended_parser() -> argparse.ArgumentParser:
             args=list(filter(lambda x: x != "-h", _))  # Drop help from args
         )
 
-        nb_info["notebook"] = nb_info["user"]["notebook"].format(**vars(user_notebook_args))
+        nb_info["notebook"] = user_notebook_path.format(**vars(user_notebook_args))
         notebook = nb_info["notebook"]
 
     cvar = nb_info.get("concurrency", {}).get("parameter", None)