[Python-Dev] one more restriction for from __future__ import ...

[Skip Montanaro]

    Jeremy> The symbol table pass detects illegal future statements by
    Jeremy> comparing the current line number against the line number of the
    Jeremy> last legal futre statement.

Why not just add a flag (default false at the start of the compilation) to
the compiling struct that tells you if you've seen a future-killer statement
already?  Then if you see a future statement the compiler can whine.

Skip