What do these changes do?

This PR addresses review comments from PR #11290 by:

• Removing redundant inner try-except block in IOBasePayload.size property - the exceptions are already handled by the outer try-except
• Updating stale test comments that referenced the bug as if it was still present
• Improving test docstrings to reflect that they verify the fix rather than demonstrate a bug

Are there changes in behavior for the user?

No behavioral changes. This is purely a code cleanup that removes redundancy while maintaining the exact same functionality.

Is it a substantial burden for the maintainers to support this?

No, this actually reduces maintenance burden by:

• Removing redundant code that could cause confusion
• Making the code flow clearer and easier to understand
• Ensuring test documentation accurately reflects the current state

Related issue number

Follow-up to #11290 (addressing review comments)
Related to #11270 (original bug fix)

Checklist

• I think the code is well written
• Unit tests for the changes exist (all existing tests pass)
• Documentation reflects the changes (no user-facing docs needed)
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
• Add a new news fragment into the CHANGES/ folder

Summary of Changes

1. Removed redundant code in aiohttp/payload.py:

# Before:
if self._start_position is None:
    try:
        self._start_position = self._value.tell()
    except (OSError, AttributeError):
        # Can't get position, can't determine size
        return None

# After:
if self._start_position is None:
    self._start_position = self._value.tell()

The inner try-except was redundant because:

• The outer try-except block in the size property already catches AttributeError and OSError
• Any exception raised by self._value.tell() will be caught by the outer handler
• Having nested try-except blocks for the same exceptions adds unnecessary complexity

2. Updated test comments in tests/test_payload.py:

• Removed comments claiming "This assertion fails!" and "This also fails!" from test_iobase_payload_size_after_reading
• Updated docstring from "demonstrates the bug" to "verifies that size calculation properly accounts for the initial file position"

3. Updated test comments in tests/test_client_functional.py:

• Updated docstring in test_file_upload_307_308_redirect from "demonstrates the bug" to "verifies that file payloads maintain correct Content-Length"

All tests continue to pass, confirming the redundant code was indeed unnecessary.