Added 'description' class attribute to every command class (to help the

'--help-commands' option).
Shuffled imports around in a few command modules to avoid expensive
  up-front import of sysconfig (and resulting delays in generating list
  of all commands).

Lib/distutils/command/build_py.py

@@ -16,6 +16,8 @@ from distutils.errors import *
 
 class BuildPy (Command):
 
+    description = "\"build\" pure Python modules (copy to build directory)"
+
     options = [('build-dir=', 'd', "directory for platform-shared files"),
               ]