Don't crash publishing on a non-bytes message key

[wbarnha]

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Description

Fixes #513.

Topic.publish_message computed the sensor key/value sizes with:

keysize=len(key) if key else 0,
valsize=len(value) if value else 0,

When a raw, unserialized non-bytes key/value reaches publish_message — e.g. an int key produced via group_by/forward — len() raises TypeError: object of type 'int' has no len(), crashing the publish. This value only feeds a sensor statistic, so it must never break sending a message.

Fix

Use the existing bytes-safe _get_len helper in faust.types.tuples (len(s) if s is not None and isinstance(s, bytes) else 0) — the same helper already used there to compute serialized key/value sizes. It returns the length for bytes and 0 otherwise.

Tests

• Added test_publish_message__non_bytes_key_does_not_crash: a PendingMessage with an int key/value goes through publish_message without raising, and the reported keysize/valsize are 0.
• Verified it catches the bug: reverting the fix makes the test fail with TypeError: object of type 'int' has no len() at faust/topics.py.
• flake8 / black --check / isort --check-only clean.

🤖 Generated with Claude Code

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Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.15%. Comparing base (3073eb9) to head (0952f80).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #695   +/-   ##
=======================================
  Coverage   94.14%   94.15%           
=======================================
  Files         104      104           
  Lines       11136    11137    +1     
  Branches     1201     1201           
=======================================
+ Hits        10484    10486    +2     
+ Misses        551      550    -1     
  Partials      101      101           

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