Edited setup.py in reuseable apps tutorial to use a context manager for open().

docs/intro/reusable-apps.txt

@@ -192,7 +192,8 @@ this. For a small app like polls, this process isn't too difficult.
        import os
        from setuptools import setup
 
-       README = open(os.path.join(os.path.dirname(__file__), 'README.rst')).read()
+       with open(os.path.join(os.path.dirname(__file__), 'README.rst')) as readme:
+           README = readme.read()
 
        # allow setup.py to be run from any path
        os.chdir(os.path.normpath(os.path.join(os.path.abspath(__file__), os.pardir)))