Fixed some bugs in the code that was doing the de-serialization of data from
json-encoded files.
One of the bugs raised an exception complaining about the Member, MailingList
and JsonStorage classes not being found when de-serializing objects that
contain instances of such classes in their attributes. I fixed it adding some
imports to the init.py file within the postman/ module
The other bug was causing an infinite loop that was triggering a RuntimeError
(maximum recursion depth exceeded) when de-serializing MailingList instances
(a call to the .load() method in the init method of the MailingList class
was causing it)
