今天早上，我在Yosemite（10.10.3）的Macbook Pro上遇到了Virtualenv的问题：
$ virtualenv ENV
New python executable in ENV/bin/python2.7
Also creating executable in ENV/bin/python
Installing setuptools, pip, wheel...
Complete output from command /Users/USER/Docu...jp/ENV/bin/python2.7 -c "import sys, pip; sys...d\"] + sys.argv[1:]))" setuptools pip wheel:
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "/usr/local/lib/python2.7/site-packages/virtualenv_support/pip-7.0.3-py2.py3-none-any.whl/pip/__init__.py", line 13, in <module>
File "/usr/local/lib/python2.7/site-packages/virtualenv_support/pip-7.0.3-py2.py3-none-any.whl/pip/utils/__init__.py", line 23, in <module>
File "/usr/local/lib/python2.7/site-packages/virtualenv_support/pip-7.0.3-py2.py3-none-any.whl/pip/_vendor/__init__.py", line 72, in load_module
File "/usr/local/lib/python2.7/site-packages/virtualenv_support/pip-7.0.3-py2.py3-none-any.whl/pip/_vendor/pkg_resources/__init__.py", line 967, in <module>
File "/usr/local/lib/python2.7/site-packages/virtualenv_support/pip-7.0.3-py2.py3-none-any.whl/pip/_vendor/pkg_resources/__init__.py", line 970, in Environment
File "/usr/local/lib/python2.7/site-packages/virtualenv_support/pip-7.0.3-py2.py3-none-any.whl/pip/_vendor/pkg_resources/__init__.py", line 260, in get_supported_platform
File "/usr/local/lib/python2.7/site-packages/virtualenv_support/pip-7.0.3-py2.py3-none-any.whl/pip/_vendor/pkg_resources/__init__.py", line 424, in _macosx_vers
AttributeError: 'module' object has no attribute 'mac_ver'
----------------------------------------
...Installing setuptools, pip, wheel...done.
Traceback (most recent call last):
File "/usr/local/bin/virtualenv-3.4", line 9, in <module>
load_entry_point('virtualenv==13.0.3', 'console_scripts', 'virtualenv-3.4')()
File "/usr/local/lib/python2.7/site-packages/virtualenv.py", line 832, in main
symlink=options.symlink)
File "/usr/local/lib/python2.7/site-packages/virtualenv.py", line 1004, in create_environment
install_wheel(to_install, py_executable, search_dirs)
File "/usr/local/lib/python2.7/site-packages/virtualenv.py", line 969, in install_wheel
'PIP_NO_INDEX': '1'
File "/usr/local/lib/python2.7/site-packages/virtualenv.py", line 910, in call_subprocess
% (cmd_desc, proc.returncode))
OSError: Command /Users/USER/Docu...jp/ENV/bin/python2.7 -c "import sys, pip; sys...d\"] + sys.argv[1:]))" setuptools pip wheel failed with error code 1
我正在使用与brew安装的virtualenv：
$ which virtualenv
/usr/local/bin/virtualenv
注意，我正在使用fishshell但是在bash下试过，我有类似的症状。卸载python，pyenv和virtualenv并开始新鲜（使用自制程序）并没有解决问题。可能是什么问题？我很挣扎。
谢谢你的帮助