Django – ModuleNotFoundError: No module named ‘djangoformsetjs’

I have a new Django app, with the following module in my settings.py:

INSTALLED_APPS = [
    'djangoformsetjs',
    'widget_tweaks',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'django_hosts',
    'rest_framework',
    'djoser',
    'app',  # Enable the inner app
    'phonenumber_field',
]

When trying to make a first upload to Heroku, it returns the error :

ModuleNotFoundError: No module named 'djangoformsetjs'

Although it works fine locally. I tried re-installing from the terminal : pip install django-formset-js

And everything seems fine :

Requirement already satisfied: django-formset-js in /Users/homepc/opt/anaconda3/lib/python3.8/site-packages (0.5.0)
Requirement already satisfied: django-jquery-js in /Users/homepc/opt/anaconda3/lib/python3.8/site-packages (from django-formset-js) (3.1.1)
Requirement already satisfied: Django in /Users/homepc/.local/lib/python3.8/site-packages (from django-formset-js) (2.2)
Requirement already satisfied: sqlparse in /Users/homepc/opt/anaconda3/lib/python3.8/site-packages (from Django->django-formset-js) (0.4.1)
Requirement already satisfied: pytz in /Users/homepc/opt/anaconda3/lib/python3.8/site-packages (from Django->django-formset-js) (2020.1)

Am i missing something in my setup please ?