Comment 9 for bug 1858890

Mainly the root cause of this bug is outdated version on RHEL/centos: https://bugzilla.redhat.com/show_bug.cgi?id=1790174 because upstream virtualenv fixed the bug somewhere in 2018.

Workaround is to avoid using `set -u` before calling activate, which can be easy to miss because that is part of the recommended bash-strict mode.