title: Python distutils error: "[directory]... doesn't exist or not a regular file"
body: <p>Let's take the following project layout:</p>
  
  <pre><code>$ ls -R .
  .:
  package  setup.py
  
  ./package:
  __init__.py  dir  file.dat  module.py
  
  ./package/dir:
  tool1.dat  tool2.dat
  </code></pre>
  
  <p>And the following content for <code>setup.py</code>:</p>
  
  <pre><code>$ cat setup.py 
  from distutils.core import setup
  
  
  setup(name='pyproj',
        version='0.1',
  
        packages=[
            'package',
        ],
        package_data={
            'package': [
                '*',
                'dir/*',
            ],
        },
       )
  </code></pre>
  
  <p>As you can see, I want to include all non-Python files in <code>package/</code> and <code>package/dir/</code> directories. However, running <code>setup.py install</code> would raise the following error:</p>
  
  <pre><code>$ python setup.py install
  running install
  running build
  running build_py
  creating build
  creating build/lib
  creating build/lib/package
  copying package/module.py -&gt; build/lib/package
  copying package/__init__.py -&gt; build/lib/package
  error: can't copy 'package/dir': doesn't exist or not a regular file
  </code></pre>
  
  <p>What gives?</p>