Replace staticfiles by static.

https://docs.djangoproject.com/en/3.0/releases/3.0/#features-removed-in-3-0

biscuit/core/templates/core/base.html

@@ -2,7 +2,7 @@
 
 {% extends "bootstrap4/bootstrap4.html" %}
 
-{% load bootstrap4 i18n menu_generator staticfiles font_awesome any_js sass_tags %}
+{% load bootstrap4 i18n menu_generator static font_awesome any_js sass_tags %}
 
 {% block bootstrap4_extra_head %}
   {% fa_css %}

biscuit/core/templates/core/group_full.html

@@ -2,7 +2,7 @@
 
 {% extends "core/base.html" %}
 
-{% load bootstrap4 font_awesome i18n staticfiles %}
+{% load bootstrap4 font_awesome i18n static %}
 {% load render_table from django_tables2 %}
 
 {% block bootstrap4_title %}{% blocktrans %}Group{% endblocktrans %} - {{ block.super }}{% endblock %}

biscuit/core/templates/core/person_card.html

 {# -*- engine:django -*- #}
 
-{% load staticfiles cropping %}
+{% load static cropping %}
 
 <div class="card shadow">
   <div class="card-header">{{ person.first_name }} {{ person.last_name }}</div>

biscuit/core/templates/core/person_full.html

@@ -2,7 +2,7 @@
 
 {% extends "core/base.html" %}
 
-{% load bootstrap4 font_awesome i18n staticfiles cropping %}
+{% load bootstrap4 font_awesome i18n static cropping %}
 {% load render_table from django_tables2 %}
 
 {% block bootstrap4_title %}{% blocktrans %}Person{% endblocktrans %} - {{ block.super }}{% endblock %}