impossible to execute a buffer with 'from future' imports

[Yaroslav Halchenko]

I guess it is a design limitation and reincarnation of
https://bugs.launchpad.net/python-mode/+bug/925586
but since its message was concerned only with the line number, I decided to file a new one.

Trying to execute a buffer (C-c C-c, or explicit execute-buffer-ipython in menu) where buffer contains code with imports from future, it simply doesn't work:

In [54]: File "/home/yoh/.tmp/ipython-23366TKY.py", line 4
    from __future__ import with_statement
SyntaxError: from __future__ imports must occur at the beginning of the file

since that buffer's code gets "extended" with additional imports by python-mode.el ... not sure what has to be done (besides parsing out the code to be executed and moving future imports ahead ...?)