How feasible is it to have support from 2.4 to 3.x? Either with or without 3to2/2to3 as part of the packaging process?

EDIT: I'd have thought upgrading the codebase to 3.x and making sure that 3to2 produces a working 2.4 version would be better than using 2to3. Thoughts?

The problem there is that 2.4's exception statements and 3.0's have two different meanings.

2.4 only supports this:

    try:
        do stuff
    except FooError, e:
        do stuff with e

3.0 and up choke on this; they interpret it as "catch exceptions of type FooError or e and do not give the exception object a name".

2.5 through 2.7 interpret like 2.4 but also support explicit parentheses to do what Python 3 does:

    try:
        do stuff
    except (FooError, BarError) as e:
        do stuff
    except (BazError, QuxError):
        do other stuff

2to3 requires that you use the new exception syntax only, to avoid confusion.

The following will work across 3 and 2 versions going back pretty far. It's necessary if you want to support pre-2.5 versions (where `as` was introduced):

    import sys
    try:
        fn()
    except (IOError, TypeError):
        err = sys.exc_info()[1]
        print(err)

http://docs.pythonsprints.com/python3_porting/py-porting.htm...

Still kind of ugly, and not something which you want to litter than Django sources. Especially if you are going to put them all back when 2.4 support is dropped.

That is precisely my goal, I think it's eminently feasible using 2to3.

I think django should include magic to fall back to 2.x version when and where 3.x is not available. May be via configuring multiple virtualenvs.

For platforms where an older version of python is standard, can that not be worked around by using virtualenv?