builder doesn't flatten nested components

[alexeiva]

I am working on a private repo with a builder workflow, and have some nested components.
I added a flattenComponents: true to config.yaml (but it should be on by default).
Fontbakery still gives me the nested components fail:

 * FAIL: The following glyphs have components which themselves are component glyphs:
	* uni1EB0
	* uni1EB4
	* uni1EAA
	* uni01C4
	* uni01C5
	* uni1EC4
	* uni01C8
	* uni01CB
	* uni1ED6
	* aacute and 196 more. [code: found-nested-components]

I tried to manually add a ufo2ft filter to the UFOs in master_ufo to unnest composites as described in fonttools/fontbakery#2961 (comment)
The generated fonts via fontmake then decompose correctly.

It looks like the flattenComponents filter isn't working with builder.

Reference:
https://github.com/googlefonts/youtube-sans/issues/12#issuecomment-800033139

[m4rc1e]

Have you upgraded your gftools? pip install --upgrade gftools

[alexeiva]

upgrading fonttools fixed the issue. thanks