[gi] return PYGLIB_MODULE_ERROR_RETURN on error
[gi] return PYGLIB_MODULE_ERROR_RETURN on error

This is to avoid some warnings when building with python 3

alexef/pygobject,MathieuDuponchelle/pygobject,GNOME/pygobject,davidmalcolm/pygobject,sfeltman/pygobject,choeger/pygobject-cmake,thiblahute/pygobject,jdahlin/pygobject,nzjrs/pygobject,thiblahute/pygobject,davibe/pygobject,Distrotech/pygobject,MathieuDuponchelle/pygobject,alexef/pygobject,MathieuDuponchelle/pygobject,pexip/pygobject,pexip/pygobject,choeger/pygobject-cmake,choeger/pygobject-cmake,Distrotech/pygobject,davidmalcolm/pygobject,GNOME/pygobject,sfeltman/pygobject,davibe/pygobject,davibe/pygobject,davibe/pygobject,sfeltman/pygobject,nzjrs/pygobject,nzjrs/pygobject,jdahlin/pygobject,GNOME/pygobject,davidmalcolm/pygobject,jdahlin/pygobject,Distrotech/pygobject,pexip/pygobject,Distrotech/pygobject,alexef/pygobject,thiblahute/pygobject