utils: don't assume all exceptions have .strerror
utils: don't assume all exceptions have .strerror

Now that we're calling the actual sensors code, there's a bug :). Not all
python Exceptions have strerror.

Signed-off-by: Tycho Andersen <6b523322678240882acbb4da5312a12d8cd0082d@tycho.pizza>

ramnes/qtile,qtile/qtile,qtile/qtile,ramnes/qtile