Warn when creating driver that points to an empty directory

[pzdkn]

Description

A warning is shown when we iterate over a driver, that points to an empty or non-existent directory.

Type of change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation update
• [ ] Refactoring including code style reformatting
• [ ] Other (please describe):

Checklist:

• [ ] I have read the contributing guideline doc (external contributors only)
• [x] Lint and unit tests pass locally with my changes
• [x] I have kept the PR small so that it can be easily reviewed
• [ ] I have made corresponding changes to the documentation
• [x] I have added tests that prove my fix is effective or that my feature works
• [ ] All dependency changes have been reflected in the pip requirement files.

[AlpAribal]

Shall we base this branch onto #72, there are some common changes in both, it might be safer to see how the changes combined work together.

[AlirezaSohofi]

Shall we base this branch onto #72, there are some common changes in both, it might be safer to see how the changes combined work together.

agree, can you please rebase this branch please @pzdkn?

[pzdkn]

I have rebased and tests for both branches pass. So we can merge #72 first, and then take care of this one @AlirezaSohofi @AlpAribal.