[Python] ipc.Message __repr__ format string not applied

[rustyconover]

Describe the bug, including details regarding any error messages, version, and platform.

Hi Arrow Team,

In Python when working with an ipc.Message if you convert it to a string with str() you get the format string, rather than the interpolated values.

pyarrow.Message
type: {self.type}
metadata length: {metadata_len}
body length: {body_len}

Seems like we're just forgetting the "f" in front of the format string.

Best wishes,

Rusty

Component(s)

Python

[Aokizy2]

Seems like we're just forgetting the "f" in front of the format string.

I found that maybe the problem is in the Message class's __repr__ method.Should I fix it?