This document describes the OpenGL 3.x (and above) deprecation model and attempts to provide advice on how to migrate your (PyOpenGL) code to be OpenGL 3.1 "legacy free" or "forward compatible".
Note, however, that most vendors have committed to providing legacy-compatible drivers for all of their products, so it is unlikely that you need to rewrite old code, though you should consider using legacy-free operations for new code.
The OpenGL 3.0 specification has for the first time introduced the concept of deprecations to the OpenGL API. Before this, OpenGL has never before deprecated any entry point in close to 17 years of development.
Originally it was intended that OpenGL 3.0 would be a "hard break" with previous OpenGL versions that would allow for a sleek and simple API for game-engine developers, sacrificing the "newbie friendliness" of the legacy API in order to better match the behaviour of modern GPU hardware. (This was the "Longs Peak" proposal, which had been eagerly awaited by the few remaining OpenGL game developers.)
The ARB, however did not implement the "Longs Peak" proposal in OpenGL 3.0, instead introducing just a set of deprecations which includes almost all of the original OpenGL API, including most entry points that OpenGL users have seen as "characterizing" the API such as those related to individual vertices and display-list behaviour. With OpenGL 3.1+ these APIs will only be available upon loading of the legacy extension.
The deprecated APIs are often referred to as "legacy" APIs, while "forward compatible" or "legacy free" is used to describe those APIs which are part of the OpenGL 3.1 subset. You should not be using legacy APIs in new code, but as noted above, the major vendors have committed to supporting the legacy APIs for the foreseeable future.
For more background, you may wish to view the PyCon 2009 presentation on the topic (note, however, that this was before the vendors committed to supporting the legacy API).
The biggest changes you will likely need to accomplish in order to be legacy free:
PyOpenGL includes a flag OpenGL.FORWARD_COMPATIBLE_ONLY, which this flag is set to True before importing OpenGL.GL then the OpenGL.GL entry points which are not forward compatible are disabled and will raise OpenGL.error.NullFunctionError exceptions on any attempt to call them.
OpenGL.FORWARD_COMPATIBLE_ONLY = True
from OpenGL.GL import *
from OpenGL.GLU import *
You would normally only set the flag once you've finished what you believe to be your whole conversion, to check that you've cleaned up all of the entry points.
Note that this flag does not attempt to disable GLU, GLUT, GLE or GLX functions which are deprecated, as we don't currently know which of those entry points will be deprecated and which will be re-implemented.