Support for robotframework 4.x

[matejc]

Add support for robotframework 4.x alongside with previous versions.

[Tattoo]

Probably have to talk face-to-face about one of the comments in the interface

[Tattoo]

__all__ should be used to declare the public interface of the module. get_keywords_from is not intended to be called from outside of Oxygen, so it should not be defined in __all__. Nor should RobotInterface for that matter; the old code was wrong as well.

[Tattoo]

Why are we changing the old RF3 interface in any way? To my mind, it should not need to change at all.

[Tattoo]

As far as I can see, these are needed only for tests. I do not quite see why we would change the interface to appease tests; rather, the tests should be re-thought to verify correct things.

[Tattoo]

Why are we exposing this new functionality? What outside of interface needs this information?

[Tattoo]

Apparently Github does not allow me to make comments/suggestions on lines that have not been changed, so let's do this the stupid way then ☹️

Please also fix the problems in RobotInterfaceBasicTests we discussed yesterday:

~line 166:

for subsuite in converted[0].suites:
            self.assertIsInstance(converted_suite, RobotSuite)
# ^ this should be:
for subsuite in converted[0].suites:
            self.assertIsInstance(subsuite, RobotSuite)

~line 171

for kw in get_keywords_from(converted_suite.tests[1]):
            self.assertIsInstance(kw, RobotKeyword)
# ^ this should be:
for kw in get_keywords_from(converted[0].tests[1]):
            self.assertIsInstance(kw, RobotKeyword)

~line 174:

for message in get_keywords_from(converted_suite.tests[1])[0].messages:
            self.assertIsInstance(message, RobotMessage)
# ^ this should be:
for message in get_keywords_from(converted[0].tests[1])[0].messages:
            self.assertIsInstance(message, RobotMessage)

[Tattoo]

Wrong quotes, should be single quotes as anywhere else

[Tattoo]

LGTM 💖

[Tattoo]

Fixes #18