checklib.py, rules3_8.py: check fails even of only the datasheet link is missing
As also the warning message
missing datasheet, please provide a datasheet link if it isn't a generic component
suggests, for some general schematic components it's meaningless to provide datasheet, but the checklib.py scripts also sets the test failed if the description, keyword fields are properly set, and only the datasheet is missing. Instead it should print the warning (maybe even without -vv), but passing the test.