Make Distribution properly abstract. Ref #419.

importlib_metadata/__init__.py

@@ -334,27 +334,7 @@ def __repr__(self) -> str:
         return f'<FileHash mode: {self.mode} value: {self.value}>'
 
 
-class DeprecatedNonAbstract:
-    # Required until Python 3.14
-    def __new__(cls, *args, **kwargs):
-        all_names = {
-            name for subclass in inspect.getmro(cls) for name in vars(subclass)
-        }
-        abstract = {
-            name
-            for name in all_names
-            if getattr(getattr(cls, name), '__isabstractmethod__', False)
-        }
-        if abstract:
-            warnings.warn(
-                f"Unimplemented abstract methods {abstract}",
-                DeprecationWarning,
-                stacklevel=2,
-            )
-        return super().__new__(cls)
-
-
-class Distribution(DeprecatedNonAbstract):
+class Distribution(metaclass=abc.ABCMeta):
     """
     An abstract Python distribution package.