title: Google App Engine dev_appserver.py IOError when importing apache_beam
body: <p>I have an App Engine application which breaks the moment I do</p>
  
  <pre><code>import apache_beam
  </code></pre>
  
  <p>I can confirm the dependencies are installed within the virtual environment the app runs in. Judging by the stack trace below it looks like it's trying to access /dev/null for some reason and it fails to.</p>
  
  <pre><code>INFO     2017-08-13 13:03:37,980 stubs.py:50] Sandbox prevented access to file "/home/raul/Downloads/google-cloud-sdk"
  INFO     2017-08-13 13:03:37,980 stubs.py:51] If it is a static file, check that `application_readable: true` is set in your app.yaml
  INFO     2017-08-13 13:03:37,980 stubs.py:50] Sandbox prevented access to file "/home/raul/Downloads/google-cloud-sdk/platform"
  INFO     2017-08-13 13:03:37,980 stubs.py:51] If it is a static file, check that `application_readable: true` is set in your app.yaml
  INFO     2017-08-13 13:03:38,260 stubs.py:50] Sandbox prevented access to file "/dev/null"
  INFO     2017-08-13 13:03:38,260 stubs.py:51] If it is a static file, check that `application_readable: true` is set in your app.yaml
  ERROR    2017-08-13 13:03:38,261 wsgi.py:263] 
  Traceback (most recent call last):
    File "/home/raul/Downloads/google-cloud-sdk/platform/google_appengine/google/appengine/runtime/wsgi.py", line 240, in Handle
      handler = _config_handle.add_wsgi_middleware(self._LoadHandler())
    File "/home/raul/Downloads/google-cloud-sdk/platform/google_appengine/google/appengine/runtime/wsgi.py", line 299, in _LoadHandler
      handler, path, err = LoadObject(self._handler)
    File "/home/raul/Downloads/google-cloud-sdk/platform/google_appengine/google/appengine/runtime/wsgi.py", line 85, in LoadObject
      obj = __import__(path[0])
    File "/home/raul/Documents/football/main.py", line 7, in &lt;module&gt;
      import apache_beam
    File "/home/raul/Documents/football/env/lib/python2.7/site-packages/apache_beam/__init__.py", line 75, in &lt;module&gt;
      import apache_beam.internal.pickler
    File "/home/raul/Documents/football/env/lib/python2.7/site-packages/apache_beam/internal/pickler.py", line 38, in &lt;module&gt;
      import dill
    File "/home/raul/Documents/football/env/lib/python2.7/site-packages/dill/__init__.py", line 27, in &lt;module&gt;
      from .dill import dump, dumps, load, loads, dump_session, load_session, \
    File "/home/raul/Documents/football/env/lib/python2.7/site-packages/dill/dill.py", line 165, in &lt;module&gt;
      FileType = type(open(os.devnull, 'rb', buffering=0))
    File "/home/raul/Downloads/google-cloud-sdk/platform/google_appengine/google/appengine/tools/devappserver2/python/stubs.py", line 260, in __init__
      raise IOError(errno.EACCES, 'file not accessible', filename)
  IOError: [Errno 13] file not accessible: '/dev/null'
  </code></pre>
  
  <p>Any ideas what might be causing this and how to fix it?</p>