Raise an explicit type error in build_py.build_packages if self.packages is None

Author: Avasam

distutils/command/build_py.py

@@ -360,7 +360,11 @@ def build_modules(self) -> None:
             self.build_module(module, module_file, package)
 
     def build_packages(self) -> None:
-        for package in self.packages or ():
+        if self.packages is None:
+            raise TypeError(
+                f"{type(self).__name__}.packages is None. Is the Distribution missing packages ?"
+            )
+        for package in self.packages:
             # Get list of (package, module, module_file) tuples based on
             # scanning the package directory.  'package' is only included
             # in the tuple so that 'find_modules()' and