diff --git a/src/core/tests/test_validators.py b/src/core/tests/test_validators.py
index 996d03542..fa862111c 100644
--- a/src/core/tests/test_validators.py
+++ b/src/core/tests/test_validators.py
@@ -50,7 +50,7 @@ def test_valid_email_setting(self):
         try:
             validators.validate_email_setting(test_value)
         except ValidationError as e:
-            error = error
+            error = e
         else:
             error = None
         self.assertIsNone(error)
diff --git a/src/identifiers/logic.py b/src/identifiers/logic.py
index 646ec67b6..20018bcfc 100755
--- a/src/identifiers/logic.py
+++ b/src/identifiers/logic.py
@@ -31,6 +31,8 @@
 
 logger = get_logger(__name__)
 
+CROSSREF_LIVE_URL = "https://doi.crossref.org/servlet/deposit"
+CROSSREF_TEST_URL = "https://test.crossref.org/servlet/deposit"
 CROSSREF_TIMEOUT_SECONDS = 30
 
 
diff --git a/src/press/models.py b/src/press/models.py
index e19c3649f..990c2617d 100755
--- a/src/press/models.py
+++ b/src/press/models.py
@@ -7,6 +7,7 @@
 import json
 import os
 import uuid
+from datetime import timezone
 
 from django.conf import settings
 from django.contrib.contenttypes.models import ContentType
diff --git a/src/submission/forms.py b/src/submission/forms.py
index 0406bb6ea..15c51a21d 100755
--- a/src/submission/forms.py
+++ b/src/submission/forms.py
@@ -6,6 +6,7 @@
 import re
 
 from django import forms
+from django.db.models import Q
 from django.utils.translation import gettext, gettext_lazy as _
 
 from submission import models
diff --git a/src/submission/logic.py b/src/submission/logic.py
index a9326291f..7a202a592 100755
--- a/src/submission/logic.py
+++ b/src/submission/logic.py
@@ -10,6 +10,7 @@
 from django.db.models import Q
 from django.shortcuts import get_object_or_404
 from django.contrib import messages
+from django.core.exceptions import ValidationError
 from django.utils.translation import get_language, gettext_lazy as _
 
 from core.forms import OrcidAffiliationForm
diff --git a/src/utils/forms.py b/src/utils/forms.py
index 4cee36998..165e65f23 100644
--- a/src/utils/forms.py
+++ b/src/utils/forms.py
@@ -11,7 +11,7 @@
 )
 from django.utils.translation import gettext_lazy as _
 from django.conf import settings
-from django.core.exceptions import ValidationError
+from django.core.exceptions import ImproperlyConfigured, ValidationError
 from django.utils.safestring import mark_safe
 
 from modeltranslation import forms as mt_forms, translator