Fix CI, add django22-py39 CI step

.gitlab-ci.yml

@@ -26,6 +26,17 @@ py38-django22:
         python3-docutils python3-pil python3-tz python3-six python3-sqlparse python3-stdnum python3-yaml python3-coreapi tox
   script: tox -e py38
 
+py39-django22:
+  stage: test
+  image: debian:bullseye
+  before_script:
+    - >
+        apt-get update &&
+        apt-get install --no-install-recommends -y
+        python3-django python3-django-casclient python3-django-reversion python3-djangorestframework
+        python3-docutils python3-pil python3-tz python3-six python3-sqlparse python3-stdnum python3-yaml python3-coreapi tox
+  script: tox -e py39
+
 linters:
   stage: quality-assurance
   image: debian:buster-backports

media/forms.py

@@ -93,9 +93,9 @@ class MediaAdminForm(ModelForm):
             side_identifier_field.widget.template_name = "media/generate_side_identifier.html"
 
     def download_data_isbndb(self, isbn):
-        api_url = "https://api2.isbndb.com/book/" + str(isbn) + "?Authorization=" + os.getenv("ISBNDB_KEY")
+        api_url = "https://api2.isbndb.com/book/" + str(isbn) + "?Authorization=" + os.getenv("ISBNDB_KEY", "")
         req = urllib.request.Request(api_url)
-        req.add_header("Authorization", os.getenv("ISBNDB_KEY"))
+        req.add_header("Authorization", os.getenv("ISBNDB_KEY", ""))
         try:
             with urllib.request.urlopen(req) as url:
                 data: dict = json.loads(url.read().decode())["book"]

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py37,py38,linters
+envlist = py37,py38,py39,linters
 skipsdist = True
 
 [testenv]