Build error on Italic fonts

[nathanielevan]

Hi, my attempts at building this font (main branch) always fail for Italics -- it emits lots of warnings of characters being unhinted, and eventually gives me this error:

ERROR: Not a valid UFO font at <repo_directory>/Italic/Instances/BoldIt/font.ufo

And this seems to happen for all the Italic fonts -- the Upright ones were built just fine, I think.
I'm currently using Python 3.11.7.

[pauldhunt]

I will look into this.