Fixed #35564 -- Improved readability of subclass identification.

django/contrib/admin/checks.py

@@ -1,4 +1,5 @@
 import collections
+import contextlib
 from itertools import chain
 
 from django.apps import apps
@@ -21,9 +22,8 @@ def _issubclass(cls, classinfo):
     issubclass() variant that doesn't raise an exception if cls isn't a
     class.
     """
-    try:
+    with contextlib.suppress(TypeError):
         return issubclass(cls, classinfo)
-    except TypeError:
     return False
 
 
@@ -34,12 +34,8 @@ def _contains_subclass(class_path, candidate_paths):
     """
     cls = import_string(class_path)
     for path in candidate_paths:
-        try:
+        with contextlib.suppress(ImportError, TypeError):
-            candidate_cls = import_string(path)
+            if issubclass(import_string(path), cls):
-        except ImportError:
-            # ImportErrors are raised elsewhere.
-            continue
-        if _issubclass(candidate_cls, cls):
                 return True
     return False
 

django/contrib/auth/checks.py

@@ -1,3 +1,4 @@
+import contextlib
 from itertools import chain
 from types import MethodType
 
@@ -15,13 +16,10 @@ def _subclass_index(class_path, candidate_paths):
     list of candidate paths. If it does not exist, return -1.
     """
     cls = import_string(class_path)
-    for index, path in enumerate(candidate_paths):
+    for i, path in enumerate(candidate_paths):
-        try:
+        with contextlib.suppress(ImportError, TypeError):
-            candidate_cls = import_string(path)
+            if issubclass(import_string(path), cls):
-            if issubclass(candidate_cls, cls):
+                return i
-                return index
-        except (ImportError, TypeError):
-            continue
     return -1