Cannot render animation Clicking Animation under Render or typing bpy.ops.render.render(animation=True) in Console won't render my simple example. Why?

I managed to render it as jpg, but will not work as video formats. I plan to to convert it to gif with ffmpeg from a H.264 or MPEG4 afterwards.

Traceback (most recent call last):
  File "/usr/lib/python3.4/code.py", line 90, in runcode
    exec(code, self.locals)
  File "&lt;blender_console&gt;", line 1, in &lt;module&gt;
  File "/usr/share/blender/scripts/modules/bpy/ops.py", line 188, in __call__
    ret = op_call(self.idname_py(), None, kw)
RuntimeError: Error: Error writing frame
Apparently Blender Found it hard to render with small number of pixels (100 * 100) with 100%, but worked OK if 1000px * 1000px with 20%, which was satisfactory for me as well. The Error message 'Error writing frame' could have been a bit more descriptive.