title: PermissionError: [Errno 13] Permission denied: '/opt/stack/.cache/pip/wheels/a7/c1/ea/cf5bd31012e735dc1dfea3131a2d5eae7978b251083d6247bd'
body: <p>I am following the instructions <a href="https://docs.openstack.org/devstack/latest/" rel="nofollow noreferrer">from this tutorial to install devstack</a>. When I type <code>./stack.sh</code>, I am receiving the following error:</p>
  
  <pre><code>Exception:
  Traceback (most recent call last):
    File "/opt/stack/requirements/.venv/lib/python3.6/site-packages/pip/basecommand.py", line 215, in main
      status = self.run(options, args)
    File "/opt/stack/requirements/.venv/lib/python3.6/site-packages/pip/commands/install.py", line 342, in run
      requirement_set.prepare_files(finder)
    File "/opt/stack/requirements/.venv/lib/python3.6/site-packages/pip/req/req_set.py", line 380, in prepare_files
      ignore_dependencies=self.ignore_dependencies))
    File "/opt/stack/requirements/.venv/lib/python3.6/site-packages/pip/req/req_set.py", line 554, in _prepare_file
      require_hashes
    File "/opt/stack/requirements/.venv/lib/python3.6/site-packages/pip/req/req_install.py", line 281, in populate_link
      self.link = self._wheel_cache.cached_wheel(self.link, self.name)
    File "/opt/stack/requirements/.venv/lib/python3.6/site-packages/pip/wheel.py", line 68, in cached_wheel
      self._cache_dir, link, self._format_control, package_name)
    File "/opt/stack/requirements/.venv/lib/python3.6/site-packages/pip/wheel.py", line 129, in cached_wheel
      wheel_names = os.listdir(root)
  PermissionError: [Errno 13] Permission denied: '/opt/stack/.cache/pip/wheels/a7/c1/ea/cf5bd31012e735dc1dfea3131a2d5eae7978b251083d6247bd'
  </code></pre>
  
  <p>What is the problem if the stack user was configured appropriately according to the tutorial?</p>