创建python2与python3虚拟环境失败的原因

ERROR: setuptools requires Python '>=3.5' but the running Python is 2.7.5

OSError: Command /root/virtualenvs/sip_python27/bin/python2.7 - setuptools pip wheel failed with error code 1

一直在setuptools上面用功夫，花了数小时也未能解决问题。

最后从https://stackoverflow.com/questions/37637872/virtualenv-oserror-setuptools-pip-wheel-failed-with-error-code-1

但我先执行pip更新，然后再执行virtualenv更新，然后就解决问题了。