Improve ImportError messages

[Paul Adamson]

The import exception messages aren't always accurate. It would be better to have something like:

try:
    from . import bcs
except ImportError as ie:
    print('PyUQTk SWIG bcs interface not imported.', ie)

[Bert Debusschere]

Hi @padamson ,

Thanks again for your suggestion. We incorporated your recommendation in recent updates to the repo, and we will continue paying attention to this.
Thanks again for your contributions!