title: Compiling cython with gcc: No such file or directory from #include "ios"
body: <p>Given a file <code>docprep.pyx</code> as simple as</p>
  <pre><code>from spacy.structs cimport TokenC
  
  print(&quot;loading&quot;)
  </code></pre>
  <p>And trying to cythonize it via</p>
  <pre><code>cythonize -3 -i docprep.pyx
  </code></pre>
  <p>I get the following error message</p>
  <pre><code>docprep.c:613:10: fatal error: ios: No such file or directory
   #include &quot;ios&quot;
            ^~~~~
  compilation terminated
  </code></pre>
  <p>As you can tell from the paths, this system has an Anaconda installation with Python 3.7. <code>numpy</code>, <code>spacy</code> and <code>cython</code> are all installed through <code>conda</code>.</p>