Improved metadata error reporting (closes #162)

climix/index.py

@@ -29,7 +29,11 @@ class Index:
             if argname in cube_mapping:
                 logging.info('Data found for input {}'.format(argname))
             else:
-                raise ValueError('No data found for input {}'.format(argname))
+                args = ", ".join(
+                    ["{}: {}".format(argname, iv.var_name)
+                     for argname, iv in self.metadata.input.items()])
+                raise ValueError('No data found for input {}. '
+                                 'Requested: ({})'.format(argname, args))
         logging.info('Adding coord categorisation.')
         coord_name = list(map(
             self.period.add_coord_categorisation, cube_mapping.values()))[0]

climix/metadata.py

@@ -377,7 +377,7 @@ def load_metadata():
         for name, idx_meta in idx_metadata.items():
             try:
                 indices[name] = build_index(idx_meta, variables, path)
-            except KeyError:
+            except (KeyError, TypeError):
                 logging.error(
                     'Metadata error for index {} from {}.'.format(name, path))
                 raise