fix flake8 errors

opentech/publicpages/admin.py

-from django.contrib import admin
+# from django.contrib import admin
 
 # Register your models here.

opentech/publicpages/models.py

 from django.conf import settings
 from django.core.paginator import EmptyPage, PageNotAnInteger, Paginator
 from django.db import models
-from django.db.models.functions import Coalesce
 
 from wagtail.wagtailadmin.edit_handlers import (
     FieldPanel,

opentech/publicpages/tests.py

-from django.test import TestCase
+# from django.test import TestCase
 
 # Create your tests here.

opentech/publicpages/views.py

-from django.shortcuts import render
+# from django.shortcuts import render
 
 # Create your views here.