Flake8 checking: disable E722: do not use bare except

Created by: ollieparanoid

Travis suddenly fails, because flake8 has a new detection rule: Using except to catch all exceptions triggers E722.

However, we only use it once and we really want to catch all exceptions, as it wraps the whole program and shows a nice error message, with the full trace in the log.

We're not the only ones hit by this: https://github.com/ManiacalLabs/BiblioPixel/issues/471