fix(issue #3199): IndexError: Replacement index 0 out of range for positional args tuple

[arunsoman]

Fixes #3199

What

autonomous fix via atomic-forge fix — CIE (code graph over MCP) localized the bug, generated a failing regression test, and forge's repair loop fixed the source against it.

Issue

IndexError: Replacement index 0 out of range for positional args tuple

The following code triggers an IndexError in astroid:

a = namedtuple('{0}', '')

AstroidError.__str__ calls self.message.format(**vars(self)) and only catches ValueError from that call. When the wrapped message itself contains a literal {0} (as collections.namedtuple's own ValueError text does for an invalid identifier), str.format raises IndexError (no positional args were supplied) instead of the expected ValueError, so the internal formatting failure leaks out as a raw IndexError rather than astroid's own error type.

Fix

astroid/exceptions.py: broaden AstroidError.__str__'s except clause from except ValueError: to except (ValueError, IndexError, KeyError): so any str.format failure on an untrusted, already-substituted message falls back to the raw message instead of crashing.

How it was verified

• CIE-generated regression test: tests/test_forge_3199.py (fails on the pre-fix code, passes on the fix)
• repair rounds: 1 failures: 1 -> 0
• repaired file(s): astroid/exceptions.py
• independently re-verified with a standalone repro script against both the pre-fix and post-fix commit (from collections import namedtuple; namedtuple('{0}', '').infer()): raises IndexError before the fix, completes cleanly after

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[correctmost]

#3203 seems like a more comprehensive fix, but it hasn't been updated in a while.

The test code in this PR seems less idiomatic too.