[data] Make the missing indices error more verbose

beat/backend/python/data.py

@@ -399,7 +399,9 @@ class CachedDataSource(DataSource):
                 )
 
             if not ok_indices:
-                raise IOError("data file `%s' have missing indices." % f_data)
+                raise IOError(
+                    "data file `%s|%s' has missing indices." % (f_data, f_chck)
+                )
 
         self.prefix = prefix
         self.unpack = unpack