>>> from django.contrib.auth.models import User
>>> from blog.models import Post
>>> user = User.objects.get(username='jamie')
>>> Post.objects.create(title='One More Post', slug='one-more-post', body='Post body', author='user')
Traceback (most recent call last):
  File "/Users/jamie/dev/venv/lib/python3.6/site-packages/django/core/management/commands/shell.py", line 69, in handle
self.run_shell(shell=options['interface'])
  File "/Users/jamie/dev/venv/lib/python3.6/site-packages/django/core/management/commands/shell.py", line 61, in run_shell
raise ImportError
ImportError

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/Users/jamie/dev/venv/lib/python3.6/site-packages/django/db/models/manager.py", line 127, in manager_method
return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/Users/jamie/dev/venv/lib/python3.6/site-packages/django/db/models/query.py", line 346, in create
obj = self.model(**kwargs)
  File "/Users/jamie/dev/venv/lib/python3.6/site-packages/django/db/models/base.py", line 468, in __init__
setattr(self, field.name, rel_obj)
  File "/Users/jamie/dev/venv/lib/python3.6/site-packages/django/db/models/fields/related.py", line 629, in __set__
self.field.rel.to._meta.object_name,
ValueError: Cannot assign "'user'": "Post.author" must be a "User" instance.