Make sure type(None) is used instead of None for the type argument of isinstance.

Using None, whether alone or in a tuple, as the second argument raises a TypeError.

Author: Sachaa-Thanasius

distutils/compilers/C/base.py

@@ -237,7 +237,7 @@ def _is_valid_macro(name, value=None):
         """
         A valid macro is a ``name : str`` and a ``value : str | None``.
         """
-        return isinstance(name, str) and isinstance(value, (str, None))
+        return isinstance(name, str) and isinstance(value, (str, type(None)))
 
     # -- Bookkeeping methods -------------------------------------------