Have django-extensions installed, can't find shell_plus

[Larz60+]

I have resolved part of the problem, and the answer is staring me in the face, but my brain is jumbled from frustration, and I'm having trouble finishing right now. At any rate, here's what has been done.

After installing django-extensions in my django virtual environment (which has been activated), here's my pip list:

Output:
... > pip list
Package           Version
----------------- -------
backcall          0.1.0  
decorator         4.3.0  
Django            1.8.19 
django-extensions 2.0.7  
ipython           6.4.0  
ipython-genutils  0.2.0  
jedi              0.12.1 
parso             0.3.1  
pexpect           4.6.0  
pickleshare       0.7.4  
pip               10.0.1 
prompt-toolkit    1.0.15 
ptyprocess        0.6.0  
Pygments          2.2.0  
pytz              2018.5 
setuptools        39.0.1 
simplegeneric     0.8.1  
six               1.11.0 
traitlets         4.3.2  
wcwidth           0.1.7

So I see it's installed in the proper place.
I then discovered (since I'm new to django, didn't immediately realize this step was necessary) that my django application had to be made aware of the package. This is done by adding

    'django-extensions',

to the end of the INSTALLED_APPS list in settings.py

So, after doing that, I try to run:

./manage.py shell_plus --notebook

and get a step further, but still not finding django-extensions:

Error:
Traceback (most recent call last):
  File "./manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "/run/media/Larz60p/Data-4TB/python/a-d/d/Django/StartupBlog/lib/python3.7/site-packages/django/core/management/__init__.py", line 354, in execute_from_command_line
    utility.execute()
  File "/run/media/Larz60p/Data-4TB/python/a-d/d/Django/StartupBlog/lib/python3.7/site-packages/django/core/management/__init__.py", line 328, in execute
    django.setup()
  File "/run/media/Larz60p/Data-4TB/python/a-d/d/Django/StartupBlog/lib/python3.7/site-packages/django/__init__.py", line 18, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/run/media/Larz60p/Data-4TB/python/a-d/d/Django/StartupBlog/lib/python3.7/site-packages/django/apps/registry.py", line 85, in populate
    app_config = AppConfig.create(entry)
  File "/run/media/Larz60p/Data-4TB/python/a-d/d/Django/StartupBlog/lib/python3.7/site-packages/django/apps/config.py", line 86, in create
    module = import_module(entry)
  File "/home/Larz60p/.pyenv/versions/3.7.0/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 965, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'django-extensions'

So, I have to leave it alone for a bit and come back to it later.
This has to be something simple, but mt tired brain is not in a state where I can recognize what's missing.