Applied patch attached to issue2550723. Problem in index page @pagesize=0 not properly propigated to previous batch link (is set to actual number of entries displayed). Using demo.py verified original issue with 0 page size. Also verified that a non-zero page size was properly propigated (values 5 and 20). Applied patch attached to issue. Verified issue with size 0 fixed. Verified that values 5 and 20 worked correctly. Updated CHANGES.txt.

# In Python 3 the "anydbm" module was renamed to be "dbm" which is now a
# package containing the various implementations. The "wichdb" module's
# whichdb() function was moved to the new "dbm" module.

try:
    # old school first because <3 had a "dbm" module too...
    import anydbm
    from whichdb import whichdb
except ImportError:
    # python 3+
    import dbm as anydbm
    whichdb = anydbm.whichdb