Comment 9 for bug 973844

> The cursor stays where it was and I don't get the strangely named new
> buffers, but the completion still doesn't work. I just get the message
> Can't find completion for "numpy.ar"

More information: If I try to complete "ex", it works fine, giving me a
buffer with a selection of words beginning with "ex". However, it fails if
I try to complete "numpy.ar", and I think I know why. My main python
buffer is called *ND 0.12*. When I press Tab, a new python buffer is
created, called *Ipython*. I assume this is where the completion is
performed, but the problem is that numpy was imported in *my* python
buffer, so trying to complete numpy symbols in a new python buffer isn't
going to work.

If the current buffer is already an ipython buffer, there's no reason to
open a new one for completion. Just use the one that's already open.