Added sctrict dependency against python3.

If python2 is the default python installation this is a lot more
portable.

Signed-off-by: Matti Möll <matti@moell.org>
Added checks for uncommon imports.

pyserial and elfutils are not verry common, an error message is best
given to indicate roughly what needs to be installed.

Signed-off-by: Matti Möll <matti@moell.org>
Merge pull request #1 from mattimo/enhanced-python-robustness

Enhanced python robustness