fix #155: remove broken import

[steko]

This is a very brutal fix for #155 that follows @lbartoletti first pull request #166 but also removes the "impossible" try..except clause where the KeyboardInterrupt would be raised.

[psolyca]

If @lbartoletti has done it and it works, I cna onyl approve ^^;

[steko]

Just to clarify: the serial download code in models/__init__.py is only used by totalopenstation-cli-connector. The GUI has a separate built-in function for serial download (almost identical). There is room for improvement, but it would be better if this was documented in the code.

[lbartoletti]

I can try this week, but AFAIRember seems ok for me.