Log Message:
py-fonttools: updated to 4.42.0

4.42.0 (released 2023-08-02)
----------------------------

- [varLib] Use sentinel value 0xFFFF to mark a glyph advance in hmtx/vmtx as non
  participating, allowing sparse masters to contain glyphs for variation \ 
purposes other
  than {H,V}VAR
- [varLib/cff] Treat empty glyphs in non-default masters as missing, thus not \ 
participating
  in CFF2 delta computation, similarly to how varLib already treats them for gvar
- Added varLib.avarPlanner script to deduce 'correct' avar v1 axis mappings based on
  glyph average weights