Test creating directory like `<property object at 0x7c7dd7379120>` under the tests directory

[hiker]

Running:

.../fab/tests$ python -m pytest -s -k  test_missing_project      ./system_tests/cui/

creates:

.../fab/tests$ ls -l fab-workspace/
total 4
drwxr-xr-x 2 joerg joerg 4096 Jun 26 19:05 '<property object at 0x7ee801b3c900>'

This likely invalid name should not be used, and the directory should be created in /tmp

[hiker]

Reason is that in fab.cui.__main__:

getattr(build_class, "project_name")

returns the property of fab.target.base

And before the actual error (abstract class cannot be created) is triggered, the code executes:

    args.project_workspace = args.workspace / args.project
    args.project_workspace.mkdir(parents=True, exist_ok=True)

Not sure about best solution.