title: simplejson error with Django 1.8.2 and dumpdata
body: <p>Command:</p>
  
  <pre><code>% ./manage.py dumpdata
  </code></pre>
  
  <p>Output: </p>
  
  <pre><code>CommandError: Unable to serialize database: cannot import name simplejson
  </code></pre>
  
  <p>zc.buildout is configured to install simplejson in the app directory.  simplejson is also present in my custom Python directory, /usr/local/python.</p>
  
  <p>Thanks for your help!</p>
  
  <p>Stack trace:</p>
  
  <pre><code>% ./manage.py dumpdata --traceback
  Traceback (most recent call last):
    File "./manage.py", line 25, in &lt;module&gt;
      sys.exit(djangorecipe.manage.main('project.settings.settings_dev'))
    File "/opt/project/eggs/djangorecipe-1.11-py2.7.egg/djangorecipe/manage.py", line 9, in main
      management.execute_from_command_line(sys.argv)
    File "/opt/project/eggs/Django-1.8.2-py2.7.egg/django/core/management/__init__.py", line 338, in execute_from_command_line
      utility.execute()
    File "/opt/project/eggs/Django-1.8.2-py2.7.egg/django/core/management/__init__.py", line 330, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "/opt/project/eggs/Django-1.8.2-py2.7.egg/django/core/management/base.py", line 390, in run_from_argv
      self.execute(*args, **cmd_options)
    File "/opt/project/eggs/Django-1.8.2-py2.7.egg/django/core/management/base.py", line 441, in execute
      output = self.handle(*args, **options)
    File "/opt/project/eggs/Django-1.8.2-py2.7.egg/django/core/management/commands/dumpdata.py", line 162, in handle
      stream=stream or self.stdout)
    File "/opt/project/eggs/Django-1.8.2-py2.7.egg/django/core/serializers/__init__.py", line 128, in serialize
      s = get_serializer(format)()
    File "/opt/project/eggs/Django-1.8.2-py2.7.egg/django/core/serializers/__init__.py", line 51, in __call__
      raise self.exception
  ImportError: cannot import name simplejson
  </code></pre>