Even though I have BR2_PACKAGE_PYTHON3_PYC_ONLY=y in my configuration, I have a lot of *.py files in /usr/lib/python3.3/. The BR2_PACKAGE_PYTHON3_PY_ONLY, BR2_PACKAGE_PYTHON3_PYC_ONLY and BR2_PACKAGE_PYTHON3_PY_PYC options should be tested and fixed as needed.
Fixed by Maxime in git (6ffab129)