Comment # 5 on bug 1044910 from Benjamin Greiner

Buildtime. Yes qgis builds bindings based on the qscintilla .sip files. Bruno's
question doesn't differentiate between runtime and buildtime, does it?

Note that there are also compiled extension modules called sip. Historically
the deprecated sip.so from python-sip <5, which should be replaced by PyQT5.sip
from python-qt5-sip (PyQt5-sip on PyPI). Those could also exist for other
packages and are runtime dependencies.

Regarding the actual Bug, I think there should not be a python-*-sip package
anymore. Just python3-*-sip packages, (and python2-*-sip if we need to support
it)