message: Allow fields to contain collections non-Nodes (i.e. strings).
diff: @@ -56,6 +56,15 @@ class PrettyPrinter(gast.NodeVisitor):
  self.result += '\n'
  def generic_visit(self, node, name=None):
  + # In very rare instances, a list can contain something other than a Node.
  + # e.g. Global contains a list of strings.
  + if isinstance(node, str):
  + if name:
  + self._print('%s%s="%s"' % (self._indent(), name, node))
  + else:
  + self._print('%s"%s"' % (self._indent(), node))
  + return
  +
  if node._fields:
  cont = ':'
  else:
  