I personally do not care about using utf8x, it has been introduced in:

  r74549 | benjamin.peterson | 2009-08-24 12:42:36 -0500 (Mon, 24 Aug 2009) | 1 line
  fix pdf building by teaching latex the right encoding package

  # Get LaTeX to handle Unicode correctly
  latex_elements = {'inputenc': r'\usepackage[utf8x]{inputenc}'}

I tried with utf8 instead and it yielded a different set of errors, so I did not tried much. But utf8-induced bugs may be easier to fix that utf8x-induced bugs, I don't know.