ImportError: cannot import name _remove_dead_weakref in django virtualenv

Question

After upgrading my Ubuntu desktop to 18.04 from 16.04, the django's virtualenv refuses to start:

(.djangoenv) mw@desktop:~/theapp$ python manage.py runserver
Traceback (most recent call last):
  File "manage.py", line 8, in <module>
    from django.core.management import execute_from_command_line
  File "/home/mw/.djangoenv/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 10, in <module>
    from django.apps import apps
  File "/home/mw/.djangoenv/local/lib/python2.7/site-packages/django/apps/__init__.py", line 1, in <module>
    from .config import AppConfig   # NOQA
  File "/home/mw/.djangoenv/local/lib/python2.7/site-packages/django/apps/config.py", line 4, in <module>
    from django.core.exceptions import AppRegistryNotReady, ImproperlyConfigured
  File "/home/mw/.djangoenv/local/lib/python2.7/site-packages/django/core/exceptions.py", line 5, in <module>
    from django.utils.encoding import force_text
  File "/home/mw/.djangoenv/local/lib/python2.7/site-packages/django/utils/encoding.py", line 10, in <module>
    from django.utils.functional import Promise
  File "/home/mw/.djangoenv/local/lib/python2.7/site-packages/django/utils/functional.py", line 1, in <module>
    import copy
  File "/usr/lib/python2.7/copy.py", line 52, in <module>
    import weakref
  File "/usr/lib/python2.7/weakref.py", line 14, in <module>
    from _weakref import (
ImportError: cannot import name _remove_dead_weakref 

On the djangoenv and outside it

$ python --version : 
`Python 2.7.12` 

Hoping to resolve the issue, I also install Python 2.7.16 on the desktop, so I get:

$ python2.7 --version
Python 2.7.16

Also when I try to install new virtualenv, I get the same error:

$ virtualenv .blaenv
Running virtualenv with interpreter /home/mw/.djangoenv/bin/python2
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/virtualenv.py", line 21, in <module>
    import logging
  File "/usr/lib/python2.7/logging/__init__.py", line 26, in <module>
    import sys, os, time, cStringIO, traceback, warnings, weakref, collections
  File "/usr/lib/python2.7/weakref.py", line 14, in <module>
    from _weakref import (
ImportError: cannot import name _remove_dead_weakref

Answers to the same error in other contexts did not help and my search led to no more clues. So really appreciate your hints.

Answer 1

As per https://askubuntu.com/questions/981663/python2-7-broken-by-weakref-import-error-please-help you probably need to recreate your virtualenv. I suspect your problem here is that you need to deactivate your current env before you try to make the new one, in order to ensure that your system python2 interpreter is the one running the virtualenv command.