Fix string coercion problem in error handling code 10:50 (#16270)

Manifests as the following stack trace
  File "/usr/local/Cellar/ansible/2.0.1.0/libexec/lib/python2.7/site-packages/ansible/utils/display.py", line 259, in error
      new_msg = u"ERROR! " + msg
      TypeError: coercing to Unicode: need string or buffer, AnsibleParserError found

lib/ansible/utils/display.py

@@ -278,7 +278,7 @@ class Display:
             wrapped = textwrap.wrap(new_msg, self.columns)
             new_msg = u"\n".join(wrapped) + u"\n"
         else:
-            new_msg = u"ERROR! " + msg
+            new_msg = u"ERROR! %s" % msg
         if new_msg not in self._errors:
             self.display(new_msg, color=C.COLOR_ERROR, stderr=True)
             self._errors[new_msg] = 1