title: pyenv fails with : ModuleNotFoundError: No module named '_ctypes' error
body: <p>I have already seen <a href="https://bugs.python.org/issue34036" rel="noreferrer">https://bugs.python.org/issue34036</a> but it did not help.</p>
  
  <p>I am trying to instal python using the followin command</p>
  
  <pre><code> pyenv install 3.7.0
  </code></pre>
  
  <p>But it throws the following error</p>
  
  <p>If the version you need is missing, try upgrading pyenv:</p>
  
  <blockquote>
    <p>Downloading Python-3.7.0.tar.xz...
    -> <a href="https://www.python.org/ftp/python/3.7.0/Python-3.7.0.tar.xz" rel="noreferrer">https://www.python.org/ftp/python/3.7.0/Python-3.7.0.tar.xz</a> Installing Python-3.7.0...</p>
    
    <p>BUILD FAILED (Ubuntu 16.04 using python-build 20180424)</p>
    
    <p>Inspect or clean up the working tree at
    /tmp/python-build.20181018113151.14218 Results logged to
    /tmp/python-build.20181018113151.14218.log</p>
    
    <p>Last 10 log lines:   File
    "/tmp/tmpecnjnct9/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/<strong>init</strong>.py",
    line 42, in </p>
    
    <p>File
    "/tmp/tmpecnjnct9/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/cmdoptions.py",
    line 16, in </p>
    
    <p>File
    "/tmp/tmpecnjnct9/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/index.py",
    line 25, in </p>
    
    <p>File
    "/tmp/tmpecnjnct9/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/download.py",
    line 39, in </p>
    
    <p>File
    "/tmp/tmpecnjnct9/pip-10.0.1-py2.py3-none-any.whl/pip/_internal/utils/glibc.py",
    line 3, in </p>
    
    <p>File
    "/tmp/python-build.20181018113151.14218/Python-3.7.0/Lib/ctypes/<strong>init</strong>.py",
    line 7, in </p>
    
    <p>from _ctypes import Union, Structure, Array ModuleNotFoundError: No module named '_ctypes'</p>
    
    <p>Makefile:1122: recipe for target 'install' failed</p>
    
    <p>make: *** [install] Error 1</p>
  </blockquote>