Fixes: https://github.com/galaxyproject/galaxy/issues/16394

Also upgrade code to Python 3.8 syntax with:

```
ack --type=python -f | grep -v '^lib/galaxy/schema/bco/\|^lib/galaxy/schema/drs/\|lib/tool_shed_client/schema/trs.*.py\|^tools/\|^.venv/\|^.tox/' | grep -v '^lib/galaxy/files/sources/\|^lib/galaxy/job_metrics/\|^lib/galaxy/objectstore/\|^lib/galaxy/tool_util/\|^lib/galaxy/util/' | xargs pyupgrade --py38-plus
```