email: set_content() raises AttributeError for memoryview with 7bit, 8bit or binary CTE #159858

Bug description

email.contentmanager.raw_data_manager explicitly registers memoryview with the same handler as bytes and bytearray, but EmailMessage.set_content() raises AttributeError for a memoryview payload when the content transfer encoding is 7bit, 8bit, or binary.

from email.message import EmailMessage

for cte in ('7bit', '8bit', 'binary'):
    message = EmailMessage()
    try:
        message.set_content(
            memoryview(b'ASCII-only message.\n'),
            maintype='application', subtype='octet-stream', cte=cte,
        )
    except AttributeError as exc:
        print(cte, exc)

All three calls report:

'memoryview' object has no attribute 'decode'

The same calls succeed with bytes or bytearray payloads. Expected: support the registered memoryview input just as for those other bytes-like inputs, preserving the payload. For 7bit, non-ASCII input should still raise UnicodeDecodeError, as it does with bytes.

The failure comes from calling data.decode() in set_bytes_content(). The existing base64 memoryview path is already covered by test_set_image_jpg in test_email.test_contentmanager.

This reproduces on CPython main at ddc647a, Python 3.16.0a1+dev, on macOS arm64.

Rechecked on October 20: the content manager from current main (4c73f50) still raises AttributeError in all three cases. The affected implementation and test files are unchanged since ddc647a.

AI assistance: Codex helped investigate the failure, prepare this report, and test a fix.

Linked PRs

• gh-159858: Fix memoryview payloads with 7bit, 8bit and binary email CTEs #159859