dev-python/urllib3-1.21.1 depends on >=dev-python/idna-2.0.0, but should be depending on >=dev-python/idna-2.0, since dev-python/idna has only 2-part version numbers and 2.0.0 > 2.0, the latter of the two being the version available in Gentoo.
commit 8f236498c6d1546346c9a2c0090f9f0f293660eb (HEAD -> master, origin/master, origin/HEAD) Author: Lars Wendler <polynomial-c@gentoo.org> Date: Tue May 16 10:34:30 2017 dev-python/urllib3: Fixed idna depend version string (bug #618616). Package-Manager: Portage-2.3.5, Repoman-2.3.2