Other imports look like they are part of the python standard distribution, and while practically we could assume any user of this has fonttools available, sometimes there are pyenv etc snafus so it seems like it should be here
For context, setup.py enumerates the dependencies to execute and dev-requirements lists additional things only someone making code changes would require (such as the formatter)
Other imports look like they are part of the python standard distribution, and while practically we could assume any user of this has fonttools available, sometimes there are pyenv etc snafus so it seems like it should be here