Defer annotation evaluation to fix RHEL import. (backport #309)

[mergify]

Description

message_filters annotates callback parameters with typing.Concatenate which was only added in Python 3.10. On Python 3.9 (RHEL 9) importing message_filters raises:

      AttributeError: module 'typing' has no attribute 'Concatenate'

This fails every message_filters Python test at collection time on the jazzy

Adding from __future__ import annotations (PEP 563) to the two affected modules stores these annotations as strings, so typing.Concatenate is never evaluated at import, restoring Python 3.9 compatibility.

Is this user-facing behavior change?

No. Annotations aren't introspected at runtime and @dataclass works with string annotations. No API/ABI change.

Did you use Generative AI?

Yes, Claude Opus 4.8 was used for the fix.

Additional Information

---

This is an automatic backport of pull request #309 done by [Mergify](https://mergify.com).

[mergify]

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[ahcorde]

Pulls: #317
Gist: https://gist.githubusercontent.com/ahcorde/4e82b27bdd41bf94ab5b2ad8c6390ab7/raw/d6cb67482f9605635b5e3c315fd59c73f83f1d96/ros2.repos
BUILD args: --packages-above-and-dependencies message_filters
TEST args: --packages-above message_filters
ROS Distro: kilted
Job: ci_launcher
ci_launcher ran: https://ci.ros2.org/job/ci_launcher/19622

• Linux
• Linux-aarch64
• Linux-rhel
• Windows