python 3.10 compat

[exterm]

[mvarnold]

For backwards compatibility, would recommend changing the import to something like this, rather than accessing the module on line 156.

try:
    from collections.abc import Mapping
except ImportError:
    from collections import Mapping

[exterm]

Fixed.

[exterm]

@mvarnold

[exterm]

@ryanjgallagher

[andyreagan]

Looks good to me (thanks!!) and looks like I could merge this but a few thoughts:

1. We don't have any github action running to confirm that the code changes work (I suppose I could just try locally)
2. More importantly, probably, I don't have access to the pypi deploy (and this is also not automated) so just merging it wouldn't help. We need Ryan to deploy the change.

I'd recommend Ryan set up both of those just to make these changes more push-button in the future.

@exterm I sent a message to Ryan on our old Slack, I'll try to get it updated if I can.