fails to build with fontmake (Expected glyph class definition or statement: got NAME condition)

[fabiangreffrath]

This happens for each of the Variable Font sources (but for the other fonts as well):

$ for f in sources/Variable\ Fonts/Monaspace\ *.glyphs ; do fontmake -o ttf -g "${f}" ; done
...
fontmake: Error: In 'sources/Variable Fonts/Monaspace Xenon Var.glyphs' -> 'master_ufo/MonaspaceXenonVar.designspace': Generating fonts from Designspace failed: <features>:186:1: Expected glyph class definition or statement: got NAME condition

Same error for all sources, no font files created.

[fabiangreffrath]

Relevant package versions:

ii  fontmake       3.10.0-2     all          Compile fonts from UFO or Glyphs to OTF/TTF
ii  python3-glyphslib 6.9.5+ds1-1        all          Library for converting between Glyphs files
ii  python3-ufo2ft        3.3.1-2        all          Bridge from UFOs to fonttools objects
ii  python3-ufolib2       0.17.1+dfsg1-1 all          Unified Font Object (UFO) fonts library