Work around a Flit bug.
There was a Flit release yesterday that broke `tox -epackage`.
See:
@@ -113,6 +113,9 @@ commands =
basepython = python3
deps =
flit
+ # This is only here to pin the transitive dependency low to work around
+ # https://github.com/pypa/flit/issues/530
+ flit_core<3.7.0
pygments
[_package]
