Widen _python_ast_exception_name return type to Optional[str]

It can fall through all branches and implicitly return None; annotate it
accordingly (and return None explicitly) instead of suppressing mypy with
type: ignore[return].

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: fhightower

d8s_python/ast_data.py

@@ -7,7 +7,7 @@
 # TODO: all of these functions where code_text is given should also be able to read a file at a given path (?)
 
 
-def _python_ast_exception_name(node: Union[ast.Raise, ast.ExceptHandler]) -> str:  # type: ignore[return]
+def _python_ast_exception_name(node: Union[ast.Raise, ast.ExceptHandler]) -> Optional[str]:
     """."""
     if hasattr(node, "exc") and node.exc:  # this handles ast.Raise nodes
         if hasattr(
@@ -40,6 +40,8 @@ def _python_ast_exception_name(node: Union[ast.Raise, ast.ExceptHandler]) -> str
     elif hasattr(node, "id"):  # this handles situations where the exception being raised is an ast.Name (e.g. "e")
         return node.id
 
+    return None
+
 
 def python_ast_raise_name(node: ast.Raise) -> Optional[str]:
     """Get the name of the exception raise by the given ast.Raise object."""