logbook.py: Add missing keyword "return"
logbook.py: Add missing keyword "return"

Bug introduced in 15bcbc29711c3b68f7da2944d7a62ecfb7316217.

glidernet/ogn-python,Meisterschueler/ogn-python,Meisterschueler/ogn-python,kerel-fs/ogn-python,glidernet/ogn-python,Meisterschueler/ogn-python,Meisterschueler/ogn-python,glidernet/ogn-python,glidernet/ogn-python