[Python] OSError: [Errno 13] Permission denied when installing virtualenv...

I don't understand why the following gives an error nor how to fix it... any help would be most appreciated. (Note that this question is similar but different than this one.)

dhcp-18-41:WakeUp6 jbs$ sudo -H virtualenv -p
/usr/local/Cellar/python@2/2.7.15 env
Password:
Running virtualenv with interpreter /usr/local/Cellar/python@2/2.7.15
Traceback (most recent call last):
File "/usr/local/bin/virtualenv", line 11, in <module>
sys.exit(main())
File "/Library/Python/2.7/site-packages/virtualenv.py", line 665, in main
popen = subprocess.Popen([interpreter, file] + sys.argv[1:], env=env)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 710, in __init__
errread, errwrite)
File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.py", line 1335, in _execute_child
raise child_exception
OSError: [Errno 13] Permission denied

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