Support Python 3.12

[icemac]

Look through the change log of Python 3.12 (once the final version is released) for potential issues which need to be handled by RestrictedPython to prevent access to otherwise forbidden data/objects.

There is no need to support new language features of Python 3.12 right now, let's see how they evolve when started being used.

Open tasks:

• make package installable and fix tests
• cut an alpha dev release (7.0a1.dev0)
• security audit
• Prepare for a new Python version after its final release as described in https://github.com/zopefoundation/RestrictedPython/blob/master/docs/contributing/index.rst#preperations-for-a-new-python-version

[d-maurer]

I have checked the items in What's new in Python 3.12 and did not find a problem for RestrictedPython.

PEP 695
new type statement -- automatically forbidden

PEP 701
extended f-strings
- embedded expressions are evaluated in the normal way, thus controlled by RestrictedPython
- provides implicit access to the format builtin (not otherwise allowed), but format being very similar to the allowed str should be safe

Interpreter improvements -- irrelevant for RestrictedPython

PEP 688 buffer protocol from Python
only available via memoryview not exposed by RestrictedPython

Standard library improvements -- no module exposed by RestrictedPython is affected

Irrelevant for RestrictedPython: security improvements, C API improvements, CPython implementation improvements, new typing features,

Nothing critical in section "Other language changes".

A few uncritical new methods in the math module.

A few uncritical changes in the random module.

Irrelevant for RestrictedPython: optimizations, CPython bytecode changes, demos and tools, deprecated.

[dataflake]

Thank you very much for taking a closer look. @icemac did you want to do your own audit? If not, Dieter's assessment sounds good to me and we could move forward with a release.

[icemac]

@d-maurer Thank you for your detailed analysis. I am now going to cut a release.

[icemac]

Just released https://pypi.org/project/RestrictedPython/7.0/