AttributeError: Can't get attribute on <module '__main__' from manage.py
# If this is an issue with pickle, it is because pickling and
# unpickling a file needs to take place within a loop with access
# to the class that ctreated the pickle in the first place as explained below:
'''
Classes (and functions) are not pickled,
only references to how to find the same class again in your program are stored.
Instances then are loaded by creating a new instance of that class and loading unpickled data into the new instance.
If you removed a class, then you can't load the pickle anymore.
'''