>=app-mobilephone/gammu-1.22.91 should have "python" USE flag to control installation of Python bindings. Homepage of dev-python/python-gammu contains: "As of 1.22.91, python-gammu is part of of Gammu tarball!" You will probably need to block dev-python/python-gammu. dev-python/python-gammu should be removed from the tree after stabilization of newer version of app-mobilephone/gammu.
I noticed that Python bindings are unconditionally installed. I will open new bug for stabilization of >=app-mobilephone/gammu-1.22.91.
You're right, it should have python USE flag.
Fixed in gammu versions 1.25.0 and 1.26.0. I've updated wammu-0.30.1 dependencies accordingly (it requires gammu python bindings).