[issue34247] PYTHONOPTIMIZE ignored in 3.7.0 when using custom launcher

[Nick Coghlan]

Nick Coghlan <ncoghlan at gmail.com> added the comment:

My comment wasn't about the 3.7.0 -> 3.7.1 fix, but rather about the fact that I suspect that 3.7.1 is now going to respect some environment variables in this case that 3.6.x ignored. I don't know for sure though, since we didn't have a test case for this until you wrote one.

So I was thinking we could include a porting note along the lines of:

===============
- starting in 3.7.1, `Py_Initialize` now consistently reads and respects all of the same environment settings as `Py_Main` (in earlier Python versions, it respected an ill-defined subset of those environment variables, while in Python 3.7.0 it didn't read any of them due to :issue:`34247`). If this behaviour is unwanted, set `Py_IgnoreEnvironmentFlag = 1` before calling `Py_Initialize`.
===============

That note then serves two purposes:

- it lets embedders know that `Py_IgnoreEnvironmentFlag = 0` just plain doesn't work properly in 3.7.0 (without their needing to find this bug for themselves)
- it lets embedders know that they may want to set `Py_IgnoreEnvironmentFlag = 1` if their embedded interpreter is now being affected by environmental settings that it ignored in previous versions

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stage: patch review -> commit review

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34247>
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