Infinite loop in `email._header_value_parser._fold_mime_parameters` when parameter names are too long

Bug report

Bug description:

Tested with 3.6 and 3.13.1

>>> import email.message
>>> message = email.message.EmailMessage()
...
>>> message.add_attachment('Hello World!', filename='hello.txt', params={130 * 'A': 'too long parameter name'})
None
>>> message.defects
[]
>>> message
<email.message.EmailMessage object at 0x7fe78ec74ec0>
>>> message.as_string()

130 characters for a media type parameter name is (a bit) more than https://datatracker.ietf.org/doc/html/rfc6838#section-4.3 allows but I didn't expect it to lead into an infinite loop. I wanted to check if the email module would catch that defect, which apparently it doesn't.

Distribution is openSUSE Leap 15.6, python 3.13.1 was installed from pyenv, 3.6 is from the distribution. The python3.11 binary from the distribution exhibits the same behaviour.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-138226
• gh-138227
• gh-138231

Riproduci il problema con email.message.EmailMessage.add_attachment e un nome di parametro di 130 caratteri, quindi esamina email._header_value_parser._fold_mime_parameters. Consulta la discussione relativa all’issue e le PR collegati prima di procedere. Il lavoro è completato quando l’input non entra più in un ciclo infinito e la copertura di regressione verifica il comportamento risultante.