fix parsing of empty memberlists #1784 & #1701

add test for list_inventory_supply
PEP8 cleanups

This will overlap with #1701, but it seems more important to implement a simple global fix for now and then evaluate whether this produces unwanted effects elsewhere.  This patch also cleans up the tests a bit, which it seems to me could not have been running correctly for quite a long time now.  Again, I have to wonder why a lack of tests is thwarting my other pull request when the integration tests aren't even being run in the first place.