dev-vcs/mercurial depends on dev-python/zstandard[python_targets_python2_7], but it can't be built
Encodes are the matter. Python 2.7 is not good at that.
By the way, Mercurial hg is still used? I don't use it mainly.
Of course I use Git you know. Maybe I am git also 😁
But some projects still use hg. Some use Bazaar...