Pillow 8.3.0 regression on convert on P images with transparency

indexed_with_transparency.png

requirements.txt

Pillow==8.3.1
pytest==6.2.4

test_convert.py

from io import BytesIO

from PIL import Image


def test_convert_p():
    with open("indexed_with_transparency.png", "rb") as f:
        data = BytesIO(f.read())

    img = Image.open(data)

    assert img.mode == "P"
    assert img.palette.mode == "RGB"
    assert img.info.get("transparency") == 0

    img2 = img.convert()

    assert img2.mode == "RGBA"