logbook.py: Fix PEP8
logbook.py: Fix PEP8

"Always use a def statement instead of an assignment statement  that
binds a lambda expression directly to a name."

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