Because it's not a developper, he does not easily understand why QGIS
Processing 2.14 does not clip his 2.5D geometry. He does not have this
issue with QGIS Processing 2.12.
So We test to clip 2.5D geometry with QGIS Processing 2.14 by commenting
geomType = layerA.dataProvider().geometryType()
if geomType in GEOM_25D:
self.tr('Input layer has unsupported geometry type
And it seems to work.
So why 2.5D geometries are not clippable in QGIS ?