Log Message:
py-fonttools: updated to 4.39.4

4.39.4 (released 2023-05-10)
----------------------------
- [varLib.interpolatable] Allow for sparse masters
- [merge] Handle differing default/nominalWidthX in CFF
- [ttLib] Add missing main.py file to ttLib package
- [ttx] Fix missing composite instructions in XML
- [ttx] Fix split tables option to work on filenames containing '%'
- [featureVars] Process lookups for features other than rvrn last
- [feaLib] support multiple substitution with classes