This _might_ be an API break. The reverse dependencies are snakemake
and congress.
snakemake recently started declaring a <=1.6.8 version restriction:
https://github.com/snakemake/snakemake/commits/a7ac40c96d6e2af47102563d0478a2220e2a2ab7
However, their reason seems to be that pulp 2.x doesn't always include a
solver. Debian python3-pulp has a hard Depends on coinor-cbc, so
wouldn't have this problem.
I am adding a << 2.0 Depends to the snakemake package for now, but am
open to removing it if it turns out to be unnecessary.
