title: Buildroot fails can't find a python module : "ImportError : Cython not found !"
body: <p>I'm trying to run a full <code>make</code> on Buildroot. I added some Python packages as hdbscan. Unfortunately, it seems Buildroot needs Cython to build hbdscan and can't find it, even though it seems to be installed...</p>
  <p>here is the error I get after running <code>make</code> :</p>
  <pre><code>&lt;path to buildroot&gt;/output/build/python-hdbscan-0.8.27/setup.py:8: UserWarning : No module named 'Cython'
  warnings.warn(e.args[0])
  &lt;path to buildroot&gt;/output/build/python-hdbscan-0.8.27/setup.py:92: UserWarning : Due to incompatibilities with Python 3.7 hdbscan nowrequires Cython to be installed in order to built it
  warnings.warn(&quot;Due to incompatibilities with Python 3.7 hdbscan now&quot;)
  ...
  raise ImportError('Cython not fuond ! Please install cython and try again')
  ImportError: Cython not fuond ! Please install cython and try again
  </code></pre>
  <p>The <code>setup.py</code> file it's trying to run does ask to <code>import cython</code> but it's supposed to be installed already. I tried every command I could see on the forums but nothing will do... As I have several versions of Python installed on my virtual machine, I thought it could be the cause of the problem but I'm not sure about that anymore... I runned a few commands like those :</p>
  <ul>
  <li><code>sudo pip install cython</code></li>
  <li><code>sudo apt --reinstall install cython</code></li>
  <li><code>sudo python3.7 -m pip install cython</code></li>
  <li><code>sudo apt-get install cython</code>
  some commands to upgrade cython, pip...
  some commands to uninstall cython then install it again...</li>
  </ul>
  <p>I don't know what to try anymore... Does anyone has an idea what I could do ?</p>