virtualenv including system python directories in path

gistfile1.txt

$ which virtualenv
/Users/kboers/.pyenv/shims/virtualenv
$ virtualenv --version
13.1.2
$ virtualenv --always-copy test_environment
New python executable in test_environment/bin/python2.7
Also creating executable in test_environment/bin/python
Installing setuptools, pip, wheel...done.
$ test_environment/bin/python
Python 2.7.10 (default, Jun  1 2015, 13:30:49) 
[GCC 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> for p in sys.path: print p
... 

/Users/kboers/test_environment/lib/python27.zip
/Users/kboers/test_environment/lib/python2.7
/Users/kboers/test_environment/lib/python2.7/plat-darwin
/Users/kboers/test_environment/lib/python2.7/plat-mac
/Users/kboers/test_environment/lib/python2.7/plat-mac/lib-scriptpackages
/Users/kboers/test_environment/lib/python2.7/lib-tk
/Users/kboers/test_environment/lib/python2.7/lib-old
/Users/kboers/test_environment/lib/python2.7/lib-dynload
/Users/kboers/.pyenv/versions/2.7.10/lib/python2.7
/Users/kboers/.pyenv/versions/2.7.10/lib/python2.7/plat-darwin
/Users/kboers/.pyenv/versions/2.7.10/lib/python2.7/lib-tk
/Users/kboers/.pyenv/versions/2.7.10/lib/python2.7/plat-mac
/Users/kboers/.pyenv/versions/2.7.10/lib/python2.7/plat-mac/lib-scriptpackages
/Users/kboers/test_environment/lib/python2.7/site-packages
>>> import traceback
>>> traceback.__file__
'/Users/kboers/.pyenv/versions/2.7.10/lib/python2.7/traceback.pyc'
>>>