title: pip install failing with: OSError: [Errno 13] Permission denied on directory
body: <p><code>pip install -r requirements.txt</code> fails with the exception below <code>OSError: [Errno 13] Permission denied: '/usr/local/lib/...</code>. What's wrong and how do I fix this? (I am trying to setup <a href="https://www.djangoproject.com" rel="noreferrer">Django</a>)</p>
  
  <pre><code>Installing collected packages: amqp, anyjson, arrow, beautifulsoup4, billiard, boto, braintree, celery, cffi, cryptography, Django, django-bower, django-braces, django-celery, django-crispy-forms, django-debug-toolbar, django-disqus, django-embed-video, django-filter, django-merchant, django-pagination, django-payments, django-storages, django-vote, django-wysiwyg-redactor, easy-thumbnails, enum34, gnureadline, idna, ipaddress, ipython, kombu, mock, names, ndg-httpsclient, Pillow, pyasn1, pycparser, pycrypto, PyJWT, pyOpenSSL, python-dateutil, pytz, requests, six, sqlparse, stripe, suds-jurko
  Cleaning up...
  Exception:
  Traceback (most recent call last):
    File "/usr/lib/python2.7/dist-packages/pip/basecommand.py", line 122, in main
      status = self.run(options, args)
    File "/usr/lib/python2.7/dist-packages/pip/commands/install.py", line 283, in run
      requirement_set.install(install_options, global_options, root=options.root_path)
    File "/usr/lib/python2.7/dist-packages/pip/req.py", line 1436, in install
      requirement.install(install_options, global_options, *args, **kwargs)
    File "/usr/lib/python2.7/dist-packages/pip/req.py", line 672, in install
      self.move_wheel_files(self.source_dir, root=root)
    File "/usr/lib/python2.7/dist-packages/pip/req.py", line 902, in move_wheel_files
      pycompile=self.pycompile,
    File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 206, in move_wheel_files
      clobber(source, lib_dir, True)
    File "/usr/lib/python2.7/dist-packages/pip/wheel.py", line 193, in clobber
      os.makedirs(destsubdir)
    File "/usr/lib/python2.7/os.py", line 157, in makedirs
      mkdir(name, mode)
  OSError: [Errno 13] Permission denied: '/usr/local/lib/python2.7/dist-packages/amqp-1.4.6.dist-info'
  </code></pre>