Revert dev-python/pyzmq py2 and net-wireless/urh update

Revert dev-python/pyzmq py2 and net-wireless/urh update

This commit reverts a revert of python2 support removal for
dev-python/pyzmq. The original commit that remove py2 support was
3635fb573254 (dev-python/pyzmq: Remove py2), committed January 28th.
Since then presumably a large number of dependencies of pyzmq have also
dropped python2 support, because after commit c3bb20728e45 (Revert
"Revert "dev-python/pyzmq: Remove py2"") from February 25 pkgcheck scan
says:

  NonsolvableDepsInStable: version 16.0.2: nonsolvable depset(depend) keyword(amd64) stable profile (default/linux/amd64/17.0) (76 total): ...
  ...
  NonsolvableDepsInStable: version 17.1.0: nonsolvable depset(depend) keyword(amd64) stable profile (default/linux/amd64/17.0) (57 total): ...

So it doesn't appear to be a trivial task to restore py2 support to
pyzmq. Unfortunately this will break net-wireless/urh (both in terms of
the software and in terms of the deptree). To keep the deptree in good
shape commit f1b680936d23 (net-wireless/urh: fix deps, probably) must
also be reverted.

This reverts commit c3bb20728e45505d9b4a48164f37bb3288577d67.
This reverts commit f1b680936d23084dc28bcab64e2cc4103a420303.

Signed-off-by: Matt Turner <mattst88@gentoo.org>