Interpolation errors check

[tphinney]

Observed behaviour

The check fails to complete with a ZeroDivisionError. The problem is very similar to that described in #4699, but the details of the error message are not identical to that one. Plus I am running the very latest Fontbakery as of a few hours ago.

NOTE that this is a pretty weird font. In many masters, some contours genuinely ARE collapsed down to a single point. This is “normal” for this font, and has to do with how the animated fill axis works. So, a rejection by Fontbakery is ok, but a div-by-zero error is not ideal.

(If you tell me I just need a custom override to not run certain checks, I will not be shocked.)

Expected behaviour

The check should complete and give better feedback.

Resources and steps needed to reproduce

This can be reproduced with the font file currently available at https://github.com/google/material-design-icons/blob/master/variablefont/MaterialSymbolsOutlined%5BFILL%2CGRAD%2Copsz%2Cwght%5D.ttf

Using:

• Python 3.11
• Fontbakery 0.12.6 (newly upgraded from 0.12.0a2)
• beziers 0.6.0 (newly upgraded from 0.5.0)

The problem is new since I upgraded Fontbakery, but I think the check itself was added since my previous Fontbakery version.