Как установить определенную версию python в виртуальное окружение?

$ which python
/usr/bin/python
$ /usr/bin/python --version
Python 2.7.10

$ which python3
/usr/local/bin/python3
$ /usr/local/bin/python3 --version
Python 3.7.0

$ virtualenv -p /usr/local/bin/python3 venv3
Running virtualenv with interpreter /usr/local/bin/python3
Using base prefix '/Library/Frameworks/Python.framework/Versions/3.7'
...
New python executable in .../venv3/bin/python3
Also creating executable in .../venv3/bin/python
Installing setuptools, pip, wheel...done.
$ ./venv3/bin/python --version
Python 3.7.0

$ virtualenv -p /usr/bin/python venv2
Running virtualenv with interpreter /usr/bin/python2.7
New python executable in .../venv2/bin/python
Installing setuptools, pip, wheel...done.
$ ./venv2/bin/python --version
Python 2.7.10
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