[python3] utils.unic: Separate PY3 _unic() with more workarounds.
[python3] utils.unic: Separate PY3 _unic() with more workarounds.

userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3