virtualenv --system-site-packages -p python3 ~/tensorflow

/Library/Frameworks/Python.framework/Versions/3.5/bin/python3
Using base prefix '/Library/Frameworks/Python.framework/Versions/3.5'
New python executable in /Users/xinhai/tensorflow/bin/python3
Also creating executable in /Users/xinhai/tensorflow/bin/python
Installing setuptools, pip, wheel...
  Complete output from command /Users/xinhai/tensorflow/bin/python3 - setuptools pip wheel:
  stringstringstringstringstringstringstringstring
Traceback (most recent call last):
  File "<stdin>", line 7, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/virtualenv_support/pip-9.0.1-py2.py3-none-any.whl/pip/__init__.py", line 5, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/logging/__init__.py", line 28, in <module>
    from string import Template
ImportError: cannot import name 'Template'


...Installing setuptools, pip, wheel...done.
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/virtualenv.py", line 2328, in <module>
    main()
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/virtualenv.py", line 713, in main
    symlink=options.symlink)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/virtualenv.py", line 945, in create_environment
    download=download,
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/virtualenv.py", line 901, in install_wheel
    call_subprocess(cmd, show_stdout=False, extra_env=env, stdin=SCRIPT)
  File "/Library/Frameworks/Python.framework/Versions/3.5/lib/python3.5/site-packages/virtualenv.py", line 797, in call_subprocess
    % (cmd_desc, proc.returncode))
OSError: Command /Users/xinhai/tensorflow/bin/python3 - setuptools pip wheel failed with error code 1