On FreeBSD 13.0-STABLE #54 stable/13-n248811-2572b6bd6bf: Sun Jan 2 22:46:43 CET 202 amd64 with port devel/py-virtualenv (py38-virtualenv-16.7.5), one will receive an error while trying to handle some python installation routines from a recent ESP32 IDF (esp-idf, https://github.com/espressif/esp-idf.git esp-idf).
I can't reproduce the error. May you try with the current version (20.16.7) of virtualenv?