check disc space

[T. Schulz]

> 
> But "if estimated_space > int(free_space * 1.05): ..." might not be
> such a bad thing when there is no other route to sanity available.

I support that.

In my current project, I know that I get 1GB of data during the next 15 
minutes or so. I would like to make sure that there is enough space 
available.

We develop on Linux but support Windows as well.
Certainly we get there if we use os.statvfs here and 
win32api.GetDiskFree there. But I belive the question is quite common 
and why shouldn't there be a os independent abstraction? Specially since 
  almost all current hardware uses some kind of file system to store things.

Thomas