After we let un-truncated float values in glyphsLib's Axis Location custom parameters (these are used to define user-space locations of masters and instances), we started getting new build failures from fonttools feaLib about "Base master not found", e.g.:

googlefonts/glyphsLib#1105

The problem seems to be feaLib VariableScalar's __repr__ as well as feaLib.parser are enforcing the axis coordinates of VariableScalars (e.g. such as those used for variable kerning or mark positioning) to be integers.

We should allow them to also be floating-point values, because the fvar's user-space coordinates are defined as Fixed in the OT spec so may well contain fractional values, and it's best to let them optionally be floats.

I'll make a PR