setup-all-chroots script failing

Since @weasel added Ubuntu impish to replace Ubuntu groovy in to the setup-dsa-chroot script (commit 266162a7), it's sending failure reports on a regular basis. The error is as follows:

[...]
E: Tried to extract package, but file already exists. Exit...
+ debootstrap --keyring /usr/share/keyrings/ubuntu-archive-keyring.gpg --include=apt,gnupg,ca-certificates --variant=buildd --arch=arm64 impish /srv/chroot/schroot-unpack/create-impish-b2z5An http://ports.ubuntu.com/ubuntu-ports /tmp/filepUerHs
+ do_cleanup
+ local cnt
+ cnt=3
++ seq 3 -1 0
+ for i in $(seq ${cnt} -1 0)
+ rm /tmp/filepUerHs
+ for i in $(seq ${cnt} -1 0)
+ umount /srv/chroot/schroot-unpack/create-impish-b2z5An/sys
umount: /srv/chroot/schroot-unpack/create-impish-b2z5An/sys: not mounted.
+ true
+ for i in $(seq ${cnt} -1 0)
+ rm -r /srv/chroot/schroot-unpack/create-impish-b2z5An
+ for i in $(seq ${cnt} -1 0)
+ :

Error: setting up impish:arm64 dchroot failed.