Make "perhaps you missed a comma?" hint in syntax warnings less cryptic

Feature or enhancement

Proposal:

Syntax warnings for code like [][""], [](), and 1[2] finish with the hint "perhaps you missed a comma?"

>>> lambda: 1[2]
<python-input-23>:1: SyntaxWarning: 'int' object is not subscriptable; perhaps you missed a comma?
<function <lambda> at 0x705dfb04b920>

When this came up in a review of currently emitted syntax warnings, it took me a moment to realise that it was suggesting the two subexpressions might have been supposed to be separate items in a sequence definition.

While I expect this would be clearer in the context of an actual warning, in isolation it felt very cryptic. Perhaps it would make sense to expand the hint to "did you miss a comma to separate sequence elements?"

Edit: Amended proposed text as @hugovk suggested

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-140893
• gh-143278

首先查看链接的 PR gh-140893 和 gh-143278，然后检查 [][""]、[]() 和 1[2] 等示例的语法警告行为。完成的标准是：警告提示清楚地说明序列元素之间可能缺少逗号，同时相关警告示例仍按预期运行。