Function completion popup writes remnant artificats to buffer

Usually occurs when using tab completion, for example see below

```
=`=jedi=0, =`= (arg1, arg2, *_*arg3*_*, arg4='patch', arg5=None) =`=jedi=`=
```

All over the line.

What happens is once the line is finished editing, a particular argument becomes highlighted (in this case arg3).

Upon first inspection it looks like the line is fine, however upon "selecting the line" (movement to the line in normal mode) the screen changes and above text is replaced in the buffer.

The function being called look something like this:

```
def helper_func(self, arg1, arg2, arg3, arg4='patch', arg5=None):
```

This isn't a visual bug either, it actually leaves text in the buffer, usually resulting in having to undo/rewrite the line (I catch it because it usually breaks my makefile)