Fix `deferred_gettext` usages as per mypy's criticism
Fix `deferred_gettext` usages as per mypy's criticism

Both of these were actual bugs which were introduced when static
formatting was switched to `deferred_gettext`.

Found by type checking, hence refs #559

agdsn/pycroft,agdsn/pycroft,agdsn/pycroft,agdsn/pycroft,agdsn/pycroft