PEP8 Indentation

Fix [PEP8](http://www.python.org/dev/peps/pep-0008/) indentation.

- 2 spaces -> 4 spaces (http://www.python.org/dev/peps/pep-0008/#indentation)
- Hanging indents ((http://www.python.org/dev/peps/pep-0008/#indentation))
- Fix ``ENOENT`` -> ``errno.ENOENT``.