Raise when get_map gets a invalid space argument

Author: AhmetNSimsek

siibra/core/parcellation.py

@@ -177,15 +177,14 @@ def get_map(self, space=None, maptype: Union[str, MapType] = MapType.LABELLED, s
             and m.parcellation.matches(self)
         ]
         if len(candidates) == 0:
-            logger.error(f"No {maptype} map in {space} available for {str(self)}")
-            return None
+            raise ValueError(f"No {maptype} map with space specification '{space}' available for {str(self)}")
         if len(candidates) > 1:
             spec_candidates = [
-                c for c in candidates if all(w.lower() in c.name.lower() for w in spec.split())
+                c for c in candidates
+                if all(w.lower() in c.name.lower() for w in spec.split())
             ]
             if len(spec_candidates) == 0:
-                logger.warning(f"'{spec}' does not match any options from {[c.name for c in candidates]}.")
-                return None
+                raise ValueError(f"'{spec}' does not match any options from {[c.name for c in candidates]}.")
             if len(spec_candidates) > 1:
                 logger.warning(
                     f"Multiple maps are available in this specification of space, parcellation, and map type.\n"