[dropbox] Fix setting oauth2 access token via env var (#1452)

storages/backends/dropbox.py

@@ -73,7 +73,9 @@ class DropboxStorage(BaseStorage):
     CHUNK_SIZE = 4 * 1024 * 1024
 
     def __init__(self, oauth2_access_token=None, **settings):
-        super().__init__(oauth2_access_token=oauth2_access_token, **settings)
+        if oauth2_access_token is not None:
+            settings["oauth2_access_token"] = oauth2_access_token
+        super().__init__(**settings)
 
         if self.oauth2_access_token is None and not all(
             [self.app_key, self.app_secret, self.oauth2_refresh_token]

tests/test_dropbox.py

@@ -6,6 +6,7 @@
 from django.core.exceptions import SuspiciousFileOperation
 from django.core.files.base import File
 from django.test import TestCase
+from django.test import override_settings
 from dropbox.files import FileMetadata
 from dropbox.files import FolderMetadata
 from dropbox.files import GetTemporaryLinkResult
@@ -54,6 +55,11 @@ def test_no_access_token(self, *args):
         with self.assertRaises(ImproperlyConfigured):
             dropbox.DropboxStorage(None)
 
+    def test_setting_access_token(self):
+        with override_settings(DROPBOX_OAUTH2_TOKEN="abc"):
+            storage = dropbox.DropboxStorage()
+            self.assertEqual(storage.oauth2_access_token, "abc")
+
     def test_refresh_token_app_key_no_app_secret(self, *args):
         inputs = {
             "oauth2_refresh_token": "foo",