Allow blank client version header for unit tests

gracedb/api/tests/utils.py

+from django.test import override_settings
+
 from rest_framework.test import APIClient
 
 from core.tests.utils import GraceDbTestBase
 
-
+# Need to allow requests without a client version header
+# to access the API for tests, unless we want to set and
+# update that header ourselves...
+@override_settings(
+    ALLOW_BLANK_USER_AGENT_TO_API=True,
+)
 class GraceDbApiTestBase(GraceDbTestBase):
     client_class = APIClient