title: Build Python as UCS-4 via pyenv
body: <p>I run into this issue <a href="https://stackoverflow.com/q/17443166/1391441">ImportError numpy/core/multiarray.so: undefined symbol: PyUnicodeUCS2_AsASCIIString</a> installing Python in a <a href="https://github.com/yyuu/pyenv-virtualenv" rel="nofollow noreferrer">pyenv-virtualenv</a> environment.</p>
  
  <p>In my case, it happens with the <code>matplotlib</code> package instead of <code>numpy</code> (as in the above question), but it's basically the same issue.</p>
  
  <p>The answer given in that question is a simple:</p>
  
  <blockquote>
    <p>Rebuild NumPy against a Python built as UCS-4.</p>
  </blockquote>
  
  <p>I don't know how to do this. In <a href="https://stackoverflow.com/a/19575808/1391441">this other question</a> it is said that one has to use:</p>
  
  <pre><code>./configure --enable-unicode=ucs4
  </code></pre>
  
  <p>but I don't know how to use that command along with <a href="https://github.com/yyuu/pyenv" rel="nofollow noreferrer">pyenv</a>.</p>
  
  <p>This issue is also mentioned in <code>pyenv</code>'s repo <a href="https://github.com/yyuu/pyenv/issues/518" rel="nofollow noreferrer">issue list</a>, and a solution given in <a href="https://github.com/yyuu/pyenv/issues/518#issuecomment-199827456" rel="nofollow noreferrer">a comment</a>. Sadly (for me) I can not understand how to apply the fix explained in said comment.</p>
  
  <p>So my question basically is: how do I build Python as UCS-4 via <code>pyenv</code>?</p>