made readme file to be opened using with context

The previous example doesn't explicitly close the opened file
object.  Although it's almost fine if the interpreter is CPython
but it could be broken if PyPy.

CPython does reference counting instead of garbage collections,
and file.__del__() closes the file itself, so files are automatically
closed when local scope ends unless these are "leaked" out of local
scope, in CPython.

PyPy does garbage collection so invocation time of __del__() methods
cannot be determined.  It means files can be unclosed even if local
scope ends and these are never leaked out.

If the `funniest` package in the example are being installed as
a dependency of another package by easy_install using PyPy,
it may cause "too many open files" error.

How to prevent this problem is to explicitly close() files or
to open files using with context (if Python 2.5+).

Many python packages in PyPI read their readme file to fill
long_description in setup.py, but this pattern without explicit
closing of file should be discouraged.

funniest/setup.py

@@ -1,9 +1,13 @@
 from setuptools import setup
 
+def readme():
+    with open('README.rst') as f:
+        return f.read()
+
 setup(name='funniest',
       version='0.1',
       description='The funniest joke in the world',
-      long_description=open('README.rst').read(),
+      long_description=readme(),
       classifiers=[
         'Development Status :: 3 - Alpha',
         'License :: OSI Approved :: MIT License',

metadata.rst

@@ -63,10 +63,14 @@ Now we can use it in setup.py like::
 
     from setuptools import setup
 
+    def readme():
+        with open('README.rst') as f:
+            return f.read()
+
     setup(name='funniest',
           version='0.1',
           description='The funniest joke in the world',
-          long_description=open('README.rst').read(),
+          long_description=readme(),
           classifiers=[
             'Development Status :: 3 - Alpha',
             'License :: OSI Approved :: MIT License',