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/command/build_py.py

@@ -388,7 +388,7 @@ def build_packages(self):
                 self.build_module(module, module_file, package)
 
     def byte_compile(self, files):
-        if hasattr(sys, 'dont_write_bytecode') and sys.dont_write_bytecode:
+        if sys.dont_write_bytecode:
             logger.warning('%s: byte-compiling is disabled, skipping.',
                            self.get_command_name())
             return