Our `jsonschema` external won't support Python 3.10, so we need to upgrade it.
It currently generates this warning:
lib/spack/external/jsonschema/compat.py:6: DeprecationWarning: Using or importing the ABCs
from 'collections' instead of from 'collections.abc' is deprecated since Python 3.3, and
in 3.10 it will stop working
This upgrades `jsonschema` to 3.2.0, the latest version with support for Python 2.7. The next
version after this (4.0.0) drops support for 2.7 and 3.6, so we'll have to wait to upgrade to it.
Dependencies have been added in prior commits.
