The pendingcaves.txt file lists caves for which we haven't yet got around to creating 
a cave_data/162n-xxx.html description file.

e.g. 
https://expo.survex.com/1626/E02
or 
https://expo.survex.com/1623/2014-bl888

the dummy data is created by
def do_pending_cave(k, url, area) in troggle/parsers/caves.py

No actual cave description file is created, just the entry in the database.

If the first part of the name is not 1623- or 1626- then the cave is assumed to be in the 1623 area.