crashes during "charm build" on zesty

[Paul Collins]

I got the following error when trying to do "charm build -o /a/b/c" on zesty:

Traceback (most recent call last):
  File "/usr/bin/charm-build", line 9, in <module>
    load_entry_point('charm-tools==2.1.2', 'console_scripts', 'charm-build')()
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 561, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2631, in load_entry_point
    return ep.load()
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2291, in load
    return self.resolve()
  File "/usr/lib/python2.7/dist-packages/pkg_resources/__init__.py", line 2297, in resolve
    module = __import__(self.module_name, fromlist=['__name__'], level=0)
  File "/usr/lib/python2.7/dist-packages/charmtools/__init__.py", line 23, in <module>
    from . import version
  File "/usr/lib/python2.7/dist-packages/charmtools/version.py", line 6, in <module>
    from charmtools import utils
  File "/usr/lib/python2.7/dist-packages/charmtools/utils.py", line 18, in <module>
    from path import path
ImportError: cannot import name path

This appears to be an incompatibility with the python-path package, which was upgraded from 8.2.1+dfsg-1 to 10.1-1 between yakkety and zesty. Downgrading to the yakkety version fixes it.