issue2550648 - partial fix for problem in this issue. Ezio Melotti reported that the expression editor allowed the user to generate an expression using retired values. To align the expression editor with the simple dropdown search item, retired values are now removed from the expression editor. Do we really want this though? Supposed a keyword is retired and I want to search for an issue with that retired keyword? Do we have a best policy document that says to remove retired keywords from all places it could possibly be used? It could be argued that the simple search dropdown is wrong and should allow selecting retired values.

# 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