History entries of issues where a value of type Date
was changed cannot be dumped:

Traceback (most recent call last):
  File
"/usr/local/lib/python2.3/site-packages/roundup/admin.py",
line 1281, in run_command
    ret = function(args[1:])
  File
"/usr/local/lib/python2.3/site-packages/roundup/admin.py",
line 1067, in do_export
    map(journals.writerow, cl.export_journals())
  File
"/usr/local/lib/python2.3/site-packages/roundup/backends/back_anydbm.py",
line 2020, in export_journals
    value = value.get_tuple()
AttributeError: 'str' object has no attribute 'get_tuple'

And indeed, value here is the serialised date, not a
Date instance.