refactor: AttributeError handling for getmro() is not needed

Internally, sphinx.util.inspect.getmro() uses `safe_getattr()` with
the `default` keyword.  Therefore it never raises AttributeError even if
the subject raises an error on accessing `__mro__` attribute.

This fixes the wrong its usage.

sphinx/ext/autodoc/__init__.py

@@ -2505,22 +2505,19 @@ class AttributeDocumenter(GenericAliasMixin, NewTypeMixin, SlotsMixin,  # type:
                 pass
 
     def get_attribute_comment(self, parent: Any, attrname: str) -> Optional[List[str]]:
-        try:
-            for cls in inspect.getmro(parent):
-                try:
-                    module = safe_getattr(cls, '__module__')
-                    qualname = safe_getattr(cls, '__qualname__')
+        for cls in inspect.getmro(parent):
+            try:
+                module = safe_getattr(cls, '__module__')
+                qualname = safe_getattr(cls, '__qualname__')
 
-                    analyzer = ModuleAnalyzer.for_module(module)
-                    analyzer.analyze()
-                    if qualname and self.objpath:
-                        key = (qualname, attrname)
-                        if key in analyzer.attr_docs:
-                            return list(analyzer.attr_docs[key])
-                except (AttributeError, PycodeError):
-                    pass
-        except (AttributeError, PycodeError):
-            pass
+                analyzer = ModuleAnalyzer.for_module(module)
+                analyzer.analyze()
+                if qualname and self.objpath:
+                    key = (qualname, attrname)
+                    if key in analyzer.attr_docs:
+                        return list(analyzer.attr_docs[key])
+            except (AttributeError, PycodeError):
+                pass
 
         return None
 

sphinx/util/inspect.py

@@ -171,10 +171,7 @@ def getannotations(obj: Any) -> Mapping[str, Any]:
 
 
 def getmro(obj: Any) -> Tuple["Type", ...]:
-    """Get __mro__ from given *obj* safely.
-
-    Raises AttributeError if given *obj* raises an error on accessing __mro__.
-    """
+    """Get __mro__ from given *obj* safely."""
     __mro__ = safe_getattr(obj, '__mro__', None)
     if isinstance(__mro__, tuple):
         return __mro__
@@ -481,12 +478,7 @@ def is_builtin_class_method(obj: Any, attr_name: str) -> bool:
     but PyPy implements it by pure Python code.
     """
     try:
-        mro = inspect.getmro(obj)
-    except AttributeError:
-        # no __mro__, assume the object has no methods as we know them
-        return False
-
-    try:
+        mro = getmro(obj)
         cls = next(c for c in mro if attr_name in safe_getattr(c, '__dict__', {}))
     except StopIteration:
         return False