MathQuill garbles compound units like degC/min in ww version 2.18

[gajennings]

bugzilla bug report #4777 (see pull request 1083) reports a bug when MathQuill deals with compound units e.g. degC/min
In this case MathQuill changes degC to a unicode "degree Celsius" symbol and that, combined with the division symbol, seems to break the answer checker. I partly fixed the problem by making "degC" and "min" into MathObject variables so that entering degC/min using MathQuill's text mode works, but it requires text mode. This seems clunky.
There doesn't seem to be a way to fix this by using the macro parserNumberWithUnits.pl because that macro requires a number with units, and this problem asks only for the units.