The `-i` flag is mixed with custom REPLs in tests

[bswck]

Bug report

Bug description:

This is an issue for a pre-existing PR #140298.

The problem lies in:

cpython/Lib/test/test_repl.py

Lines 359 to 362 in a8edca6

	class TestAsyncioREPL(unittest.TestCase):
	def test_multiple_statements_fail_early(self):
	user_input = "1 / 0; print(f'afterwards: {1+1}')"
	p = spawn_repl("-m", "asyncio")

(I wrote this 😬)

It resorts to spawn_repl that adds -i on top of -m asyncio:

cpython/Lib/test/test_repl.py

Lines 44 to 45 in a8edca6

	cmd_line = [stdin_fname, '-I', '-i']
	cmd_line.extend(args)

Mixing -i with -m asyncio causes the asyncio REPL to launch first, and then a regular Python REPL--right after the former exits.
This is an expected outcome when -i and -m asyncio are mixed.
I didn't intend this result of the current setup--we want -i^<custom repl args> to run a REPL when testing without a PTY.

CPython versions tested on:

3.15

Operating systems tested on:

Linux

Linked PRs

• gh-140438: Properly run the asyncio REPL in REPL tests #140298
• [3.14] gh-140438: properly run the asyncio REPL tests (GH-140298) #140507
• [3.13] gh-140438: properly run the asyncio REPL tests (GH-140298) #140508

[bswck]

@ZeroIntensity (mentorship) Suggesting labels: topic-repl, tests, 3.13, 3.14, 3.15.