trace i see when overwriting WidgetWrap.render

gistfile1.txt

with

```
def render(size, focus=False):
     return urwid.WidgetWrap.render(size, focus=focus)
```

-----------------------------------------------

  File "/home/pazz/.local/lib/python2.7/site-packages/alot/buffers.py", line 37, in render
    return self.body.render(size, focus)
  File "/home/pazz/.local/lib/python2.7/site-packages/urwid-1.2.0_dev-py2.7-linux-x86_64.egg/urwid/widget.py", line 141, in cached_render
    canv = fn(self, size, focus=focus)
  File "/home/pazz/.local/lib/python2.7/site-packages/urwid-1.2.0_dev-py2.7-linux-x86_64.egg/urwid/widget.py", line 1751, in render
    canv = get_delegate(self).render(size, focus=focus)
  File "/home/pazz/.local/lib/python2.7/site-packages/urwid-1.2.0_dev-py2.7-linux-x86_64.egg/urwid/widget.py", line 141, in cached_render
    canv = fn(self, size, focus=focus)
  File "/home/pazz/.local/lib/python2.7/site-packages/urwid-1.2.0_dev-py2.7-linux-x86_64.egg/urwid/listbox.py", line 475, in render
    focus_canvas = focus_widget.render((maxcol,), focus=focus)
  File "/home/pazz/.local/lib/python2.7/site-packages/urwid-1.2.0_dev-py2.7-linux-x86_64.egg/urwid/widget.py", line 141, in cached_render
    canv = fn(self, size, focus=focus)
  File "/home/pazz/.local/lib/python2.7/site-packages/urwid-1.2.0_dev-py2.7-linux-x86_64.egg/urwid/container.py", line 2055, in render
    focus = focus and self.focus_position == i)
  File "/home/pazz/.local/lib/python2.7/site-packages/urwid-1.2.0_dev-py2.7-linux-x86_64.egg/urwid/widget.py", line 141, in cached_render
    canv = fn(self, size, focus=focus)
TypeError: render() got multiple values for keyword argument 'focus'