setuptools resolves the dynamic version attr by reading geonode.__version__
directly. That attribute is a tuple (e.g. (5, 1, 0, 'final', 0)); setuptools
normalises a non-string attr by joining it with dots, producing an invalid
PEP 440 version like '5.1.0.final.0' and breaking the wheel build.

Expose a plain string attribute __version_str__ = get_version() in
geonode/__init__.py and point the dynamic version at it, so setuptools reads
an already-normalised version string (e.g. '5.1.0').

(cherry picked from commit a2dda2e)