Tests broken by fix for CVE-2023-27043

[jackwilsdon]

Running the following:

$ pytest tests/test_message.py -k 'test_unicode_sender_tuple or test_unicode_sender' 

Gives the following 2 test failures:

============================= test session starts ==============================
platform linux -- Python 3.11.10, pytest-8.3.2, pluggy-1.5.0
rootdir: /home/jack/Development/flask-mail
configfile: pyproject.toml
collected 38 items / 36 deselected / 2 selected

tests/test_message.py FF                                                 [100%]

=================================== FAILURES ===================================
__________________________ test_unicode_sender_tuple ___________________________

app = <Flask 'conftest'>, mail = <flask_mail.Mail object at 0x7f2736863b50>

    def test_unicode_sender_tuple(app: Flask, mail: Mail) -> None:
        msg = Message(
            subject="subject",
            sender=("ÄÜÖ → ✓", "from@example.com>"),
            recipients=["to@example.com"],
        )
    
>       assert (
            "From: =?utf-8?b?w4TDnMOWIOKGkiDinJM=?= <from@example.com>" in msg.as_string()
        )
E       assert 'From: =?utf-8?b?w4TDnMOWIOKGkiDinJM=?= <from@example.com>' in 'Content-Type: text/plain; charset="utf-8"\r\nMIME-Version: 1.0\r\nContent-Transfer-Encoding: 7bit\r\nSubject: subject...e.com\r\nDate: Thu, 17 Oct 2024 23:02:26 +0100\r\nMessage-ID: <172920254627.709841.8859146253803791520@frmwrk>\r\n\r\n'
E        +  where 'Content-Type: text/plain; charset="utf-8"\r\nMIME-Version: 1.0\r\nContent-Transfer-Encoding: 7bit\r\nSubject: subject...e.com\r\nDate: Thu, 17 Oct 2024 23:02:26 +0100\r\nMessage-ID: <172920254627.709841.8859146253803791520@frmwrk>\r\n\r\n' = as_string()
E        +    where as_string = <flask_mail.Message object at 0x7f273684d210>.as_string

tests/test_message.py:423: AssertionError
_____________________________ test_unicode_sender ______________________________

app = <Flask 'conftest'>, mail = <flask_mail.Mail object at 0x7f2736860f10>

    def test_unicode_sender(app: Flask, mail: Mail) -> None:
        msg = Message(
            subject="subject",
            sender="ÄÜÖ → ✓ <from@example.com>>",
            recipients=["to@example.com"],
        )
    
>       assert (
            "From: =?utf-8?b?w4TDnMOWIOKGkiDinJM=?= <from@example.com>" in msg.as_string()
        )
E       assert 'From: =?utf-8?b?w4TDnMOWIOKGkiDinJM=?= <from@example.com>' in 'Content-Type: text/plain; charset="utf-8"\r\nMIME-Version: 1.0\r\nContent-Transfer-Encoding: 7bit\r\nSubject: subject...e.com\r\nDate: Thu, 17 Oct 2024 23:02:26 +0100\r\nMessage-ID: <172920254629.709841.4673263625146708117@frmwrk>\r\n\r\n'
E        +  where 'Content-Type: text/plain; charset="utf-8"\r\nMIME-Version: 1.0\r\nContent-Transfer-Encoding: 7bit\r\nSubject: subject...e.com\r\nDate: Thu, 17 Oct 2024 23:02:26 +0100\r\nMessage-ID: <172920254629.709841.4673263625146708117@frmwrk>\r\n\r\n' = as_string()
E        +    where as_string = <flask_mail.Message object at 0x7f2736861e90>.as_string

tests/test_message.py:435: AssertionError
=========================== short test summary info ============================
FAILED tests/test_message.py::test_unicode_sender_tuple - assert 'From: =?utf...
FAILED tests/test_message.py::test_unicode_sender - assert 'From: =?utf-8?b?w...
======================= 2 failed, 36 deselected in 0.04s =======================

This is caused by email.utils.parseaddr returning an empty tuple for the emails used in those tests:

$ python3 -c 'import email.utils; print(email.utils.parseaddr("ÄÜÖ → ✓ from@example.com>"))'
('', '')

This wasn't the case prior to the CVE fix released in the below Python versions.

Environment:

• Python version: 3.9.20 / 3.10.15 / 3.11.10 / 3.12.6 / 3.13.0
• Flask-Mail version: 0.10.0
• Flask version: 3.0.3