CLI v.0.9.3 index out of range execution error when a non-standard codelist term includes the def:ExtendedValue="Yes" attribute.
See define_xml_reader_2_1.py, get_extensible_codelist_mappings.
Note: I tested with a revised define.xml document by removing the incorrectly provided attribute and it worked. However, that should be part of a separate validation rule and not an execution error.
I dont'know if it was happening with prior versions.