Listing tests issue in Cirrus CI with latest Avocado

[clebergnu]

As it can be seen in this Cirrus CI job:

python3 -m avocado -V list --vt-save-config=/tmp/config --vt-type=$VT_TYPE -- boot | tee /tmp/list
No python imaging library installed. Screendump and Windows guest BSOD detection are disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
Virsh executable not set or found on path, virsh module will not function normally
No python imaging library installed. PPM image conversion to JPEG disabled. In order to enable it, please install python-imaging or the equivalent for your distro.
Type Test Tag(s)
Resolver             Reference Info
avocado-instrumented boot      File "boot" does not end with ".py"
avocado-vt           boot      Unsupported kind of runnable: avocado-vt
python-unittest      boot      File "boot" does not end with ".py"
exec-test            boot      File "boot" does not exist or is not a executable file
tap                  boot      File "boot" does not exist or is not a executable file
TEST TYPES SUMMARY
==================
test $(wc -l < /tmp/list) -eq 1

It fails to produce a list of the 'boot' test(s), with a very weird message that at first sight, should only be given while attempting to run an avocado-vt test (and not during resolution).