Unable to use some specific kinds of font variants (ExtraBold, Heavy, etc.)

[baruchel]

Some variants of installed fonts can't be used
Trying to use Extrabold or Heavy variants of correctly installed Iosevka fonts make rst2pdf fall back to the regular variant.

The fonts are loaded from the stylesheet in the fontName attribute with the Name-Variant syntax, and it actually works well for standard variant names, but trying to do the same with Extrabold or Heavy doesn't work. Many workarounds are tried (putting the variant name in the font name and/or the variant name), but none could help loading the font.

Fonts are correctly listed with fc-list.

[lornajane]

I think the font loading only accepts four weights (normal, bold, italic and bolditalic), I can replicate this problem.