When logging, indicate whether exception was ignored by blivet.

Other tools examine the log to determine if there was a failure. The
IGNORED flag indicates that, while there was a traceback, blivet felt
able to ignore it, and so the tools should not treat the existance of this
traceback as a sign of failure.

Signed-off-by: mulhern <amulhern@redhat.com>
New version: 0.59
Remove whitespace
Use module six instead of compat.py, additional unicode fixes