Bumped pkgrel.
greenlet is a dependency of gevent (pulled by this PKGBUILD); ujson is optional as of gevent-websocket v0.9.3, moved to optdepends.
I'm not convinced python2-versiontools is appropriate for makedepends (it's only for the setup script to function) as pip should use it only briefly during install as per setup_requires:

https://pythonhosted.org/setuptools/setuptools.html