IOError does not have property 'message' in Python 3. Instead of
attempting to access it, just use the string representation of
the exception object. This produces the error message possibly combined
with additional arguments in both Python 2 and Python 3.
Task-number: QTBUG-83488
Pick-to: 6.2
Change-Id: Icb198a409e7f80b832e474d8390b770fdeacc6c2
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>