This package is depending on dev-python/mysql-python which is broken and abandoned by upstream. You should attempt to switch to dev-python/mysqlclient which is a continued fork of mysql-python. Please test that it works like it's supposed to, so broken mysql-python can be last-rited and removed from the tree.
I see there's a condition, mysql? ( || ( dev-python/mysql-python[${PYTHON_USEDEP}] dev-python/mysqlclient[${PYTHON_USEDEP}] ) I'll update the condition while removing last-rited package.