fixup! add a regionmapping to the config

src/concordia/settings.py

@@ -4,6 +4,7 @@
 import yaml
 from attrs import define
 from cattrs import structure, transform_error
+from cattrs.errors import ClassValidationError
 
 
 Pathy = str | Path
@@ -52,7 +53,7 @@ class Settings:
     def resolve_paths(config):
         def expand(path):
             if path[0] == "$":
-                reference, relative = path.split("/", 1)
+                reference, relative = path[1:].split("/", 1)
                 return expand(config[reference]) / relative
 
             return Path(path).expanduser()
@@ -80,5 +81,5 @@ def from_config(cls, config_path: Pathy = "config.yaml", **overwrites) -> Self:
         # TODO might want to replace with merge for nested dictionaries
         try:
             return structure(cls.resolve_paths(config | overwrites), cls)
-        except Exception as exc:
+        except ClassValidationError as exc:
             raise ValueError(", ".join(transform_error(exc, path="config"))) from None