RFC: Python maintenance policy

[Lawrence Velázquez]

Maintaining old versions of CPython that aren't supported upstream is
annoying and a poor use of our time, so I'd like to propose
a maintenance policy. After we chit-chat about it, I'll write something
up on the wiki (hopefully a little clearer) and inform macports-users.

The term "replaced by" signifies using the "replaced_by" Portfile option
to obsolete a port.

The term "X.Y" refers to the CPython series in question.

The term "A.B" refers to the latest release on X.Y's development branch
*at the time of deprecation*. (The policy will ignore new upstream
releases made during the deprecation period.)

The term "M.N" refers to an arbitrary release between X.Y and A.B.


====== POLICY ======

The deprecation period for the X.Y series begins when the pythonXY port
is updated to the final upstream bugfix release and ends when the port
is replaced by pythonAB. Upstream security fixes may still be applied to
pythonXY during this period.

Once pythonXY is deprecated:

  - New ports must not use pythonXY or create pyXY subports.

  - After all dependents have been migrated, ports that use pythonXY
    must switch to pythonAB.

  - After all dependents have been retired, pyXY-foo ports must be
    replaced by pyAB-foo. A pyXY-foo module that has been subsumed into
    the A.B standard library must be replaced by pythonAB, although any
    intermediate pyMN-foo ports may remain.

  - Retired subports must be moved to a graveyard metaport so that
    subsequent changes to their superports do not trigger spurious
    failures on the buildslaves.

The pythonXY port is replaced by pythonAB one to two years after it is
updated to the final upstream bugfix release. At this point, the
deprecation period concludes, and the X.Y series is considered retired.


===== SCHEDULE =====

My short-term goal is to cut us back to the two most recent releases on
each CPython dev branch. Thus, the following series are deprecated and
will be retired on 1 January 2015:

- 2.4 series
- 2.5 series
- 3.1 series
- 3.2 series

The following series have also seen their final upstream bugfix release
and should thus be considered deprecated. They will be retired on
1 January 2016:

- 2.6 series
- 3.3 series

The following series seems to be undead and/or immortal. We'll pencil it
in for Ragnarok or thereabouts:

- 2.7 series

====================


Comments welcome.

vq