Error when running collectstatic (manage.py)

When following the installation & setup steps for Askbot as described in the Askbot documentation (chapter "Initial Configuration of Askbot"), I run into the following error when trying to run python manage.py collectstatic after having completed askbot-setup (see last line of console output below... there is a metaclass conflict):


$ python manage.py collecstatic
Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/django/core/management/__init__.py", line 354, in execute_from_command_line
    utility.execute()
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/django/core/management/__init__.py", line 328, in execute
    django.setup()
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/django/apps/registry.py", line 108, in populate
    app_config.import_models(all_models)
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/django/apps/config.py", line 198, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/lib/python2.7/importlib/__init__.py", line 37, in import_module
    __import__(name)
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/askbot/models/__init__.py", line 2, in <module>
    startup_procedures.run()
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/askbot/startup_procedures.py", line 1086, in run
    run_startup_tests()
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/askbot/startup_procedures.py", line 1012, in run_startup_tests
    test_modules()
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/askbot/startup_procedures.py", line 289, in test_modules
    try_import(mod_name, pip_path)
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/askbot/startup_procedures.py", line 209, in try_import
    load_module(module_name)
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/askbot/utils/loading.py", line 23, in load_module
    return __import__(mod_path, globals(), locals(), [], -1)
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/picklefield/__init__.py", line 5, in <module>
    from picklefield.fields import PickledObjectField # reexport
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/picklefield/fields.py", line 79, in <module>
    class PickledObjectField(_get_subfield_superclass()):
  File "/home/caap-askbot-admin/.local/lib/python2.7/site-packages/django/db/models/fields/subclassing.py", line 24, in __new__
    new_class = super(SubfieldBase, cls).__new__(cls, name, bases, attrs)
TypeError: Error when calling the metaclass bases
    metaclass conflict: the metaclass of a derived class must be a (non-strict) subclass of the metaclasses of all its bases

Has anyone encountered the same or similar problem?

I am running Ubuntu 16.04 LTS and Python 2.7.12...