title: IPOPT optimizer signal handler TypeError
body: <p>I am getting the following error while using IPOPT from pyOptSparse in OpenMDAO.
  I followed pyoptsparse documentations to install pyOptSparse with IPOPT which went very smooth. 
  The SLSQP optimizer works perfect but IPOPT gives this error. 
  Thank you
  <a href="https://i.stack.imgur.com/cAf23.jpg" rel="nofollow noreferrer">1</a></p>