I just ran into the exact same bug. For me it happens around 50% of the times I try to create a virtualenv.
The version of python3-virtualenv installed is 20.4.0+ds-1. Daniel -- System Information: Debian Release: 11.0 APT prefers unstable APT policy: (500, 'unstable') Architecture: amd64 (x86_64) Foreign Architectures: i386 Kernel: Linux 5.10.0-7-amd64 (SMP w/12 CPU threads) Kernel taint flags: TAINT_OOT_MODULE, TAINT_UNSIGNED_MODULE Locale: LANG=de_DE.UTF-8, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8), LANGUAGE not set Shell: /bin/sh linked to /bin/dash Init: systemd (via /run/systemd/system) LSM: AppArmor: enabled Versions of packages python3-virtualenv depends on: ii python-pip-whl 20.3.4-2 ii python3 3.9.2-3 ii python3-appdirs 1.4.4-1 ii python3-distlib 0.3.1-1 ii python3-distutils 3.9.2-1 ii python3-filelock 3.0.12-2 ii python3-importlib-metadata 1.6.0-2 ii python3-pip 20.3.4-2 ii python3-pkg-resources 52.0.0-3 ii python3-six 1.16.0-1 python3-virtualenv recommends no packages. python3-virtualenv suggests no packages. -- no debconf information