make sure static subdir 404s correctly

before each request, we put the current service on the flask session,
except for with the static folder, cos it's not needed.... except, if
we 404, then we return the 404 template, which checks if you're logged
in or not to display different nav bar items. This was crashing when
current_service wasn't set, so we now set it.

also cleaned up some imports and stuff in test files

tests/app/main/views/test_jobs.py

@@ -1,4 +1,3 @@
-import csv
 import json
 import uuid
 from urllib.parse import urlparse, quote, parse_qs
@@ -7,8 +6,6 @@ import pytest
 from flask import url_for
 from bs4 import BeautifulSoup
 
-from app import utils
-from io import StringIO
 from app.main.views.jobs import get_time_left, get_status_filters
 from tests import notification_json
 from freezegun import freeze_time
@@ -117,7 +114,7 @@ def test_should_show_page_for_one_job(
         service_one['id'],
         fake_uuid,
         status=expected_api_call
-        )
+    )
 
 
 def test_get_jobs_should_tell_user_if_more_than_one_page(
@@ -262,7 +259,6 @@ def test_should_show_updates_for_one_job_as_json(
     mocker,
     fake_uuid,
 ):
-    job_json = mock_get_job(service_one['id'], fake_uuid)['data']
     response = logged_in_client.get(url_for('main.view_job_updates', service_id=service_one['id'], job_id=fake_uuid))
 
     assert response.status_code == 200
@@ -386,7 +382,6 @@ def test_should_show_notifications_for_a_service_with_next_previous(
         page=2
     ))
     assert response.status_code == 200
-    content = response.get_data(as_text=True)
     page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')
     next_page_link = page.find('a', {'rel': 'next'})
     prev_page_link = page.find('a', {'rel': 'previous'})