Packaging cleanup: remove conditionals for < 2.6 support.

PEP 370 features and sys.dont_write_bytecode are always available
in 3.3; the distutils2 backport still has the conditionals.

I also renamed an internal misnamed method and fixed a few things
(“packaging2” name, stray print, unused import, fd leak).

Lib/packaging/tests/test_command_build_py.py

@@ -99,8 +99,6 @@ class BuildPyTestCase(support.TempdirManager,
             os.chdir(cwd)
             sys.stdout = old_stdout
 
-    @unittest.skipUnless(hasattr(sys, 'dont_write_bytecode'),
-                         'sys.dont_write_bytecode not supported')
     def test_dont_write_bytecode(self):
         # makes sure byte_compile is not used
         pkg_dir, dist = self.create_dist()