The version function in setup.py doesn't work on pip install

[Terry Jones]

Not sure what's going on here. This works in other projects.

$ pip install rpnpy
Collecting rpnpy
  Downloading https://files.pythonhosted.org/packages/5b/b3/c9a9ce4ff33f7fb6afba9fdd0e1c93f1f7accbeaca58745c7bb60db750bf/rpnpy-1.0.26.tar.gz
    ERROR: Complete output from command python setup.py egg_info:
    ERROR: Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-nakh2gxa/rpnpy/setup.py", line 27, in <module>
        version=version(),
      File "/tmp/pip-install-nakh2gxa/rpnpy/setup.py", line 16, in version
        with open(init) as fp:
    FileNotFoundError: [Errno 2] No such file or directory: '/tmp/pip-install-nakh2gxa/rpnpy/rpnpy/__init__.py'
    ----------------------------------------
ERROR: Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-nakh2gxa/rpnpy/