Vendor packaging==26

[woodruffw]

This is like #196 but vendors an even newer packaging, to hopefully unblock #262 🙂

[di]

I think this needs the addition of https://pypi.org/p/packaging-legacy so we can handle legacy versions, similar to #196.

[woodruffw]

I think this needs the addition of https://pypi.org/p/packaging-legacy so we can handle legacy versions, similar to #196.

Makes sense, I can poke at that tomorrow!