Virtualenv: Error al ejecutar virtualenv venv --python python3 en una instalación nueva de Yosemite

Pasos para reproducir::

brew install python python3
pip install virtualenv
virtualenv venv --python python3

Este es el stacktrace:

Running virtualenv with interpreter /usr/local/bin/python3
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/virtualenv.py", line 14, in <module>
    import shutil
  File "/usr/local/Cellar/python3/3.4.3_2/Frameworks/Python.framework/Versions/3.4/lib/python3.4/shutil.py", line 11, in <module>
    import fnmatch
  File "/usr/local/Cellar/python3/3.4.3_2/Frameworks/Python.framework/Versions/3.4/lib/python3.4/fnmatch.py", line 15, in <module>
    import functools
  File "/usr/local/Cellar/python3/3.4.3_2/Frameworks/Python.framework/Versions/3.4/lib/python3.4/functools.py", line 21, in <module>
    from collections import namedtuple
  File "/usr/local/Cellar/python3/3.4.3_2/Frameworks/Python.framework/Versions/3.4/lib/python3.4/collections/__init__.py", line 17, in <module>
     from reprlib import recursive_repr as _recursive_repr
  File "/usr/local/lib/python2.7/site-packages/reprlib/__init__.py", line 7, in <module>
    raise ImportError('This package should not be accessible on Python 3. '
ImportError: This package should not be accessible on Python 3. Either you are trying to run from the python-future src folder or your installation of python-future is corrupted.