PyYAML 3.11 wheel is not Python3-compatible

[nsoranzo]

I'm trying to run Galaxy unit tests in a Python3 virtualenv and this is the first thing that broke:

Collecting PyYAML==3.11 (from -r requirements.txt (line 4))
  Downloading https://wheels.galaxyproject.org/packages/PyYAML-3.11.tar.gz (138kB)
    100% |████████████████████████████████| 143kB 1.2MB/s 
    Complete output from command python setup.py egg_info:
    running egg_info
    creating pip-egg-info/PyYAML.egg-info
    writing top-level names to pip-egg-info/PyYAML.egg-info/top_level.txt
    writing pip-egg-info/PyYAML.egg-info/PKG-INFO
    writing dependency_links to pip-egg-info/PyYAML.egg-info/dependency_links.txt
    writing manifest file 'pip-egg-info/PyYAML.egg-info/SOURCES.txt'
    error: package directory 'lib3/yaml' does not exist

The reason seems to be that https://wheels.galaxyproject.org/packages/PyYAML-3.11.tar.gz is missing files and dirs with respect to https://pypi.python.org/packages/75/5e/b84feba55e20f8da46ead76f14a3943c8cb722d40360702b2365b91dec00/PyYAML-3.11.tar.gz#md5=f50e08ef0fe55178479d3a618efe21db

Maybe while fixing this we can also move to the latest version 3.12 .