Fix AttributeError when extracting tags from pika

[ghost]

Resolves #354.

Also removes duplicate call to span.set_tag as it seems to already be done at _extract_broker_tags.

[Ferenc-]

Hi,
Thank you for your great contribution!
I noticed, that the main reason why we can have such bugs, is that we have no unit tests,
which would test with BlockingConnection.
Even our TestPikaBlockingChannel class only uses Connection and no BlockingConnection.
Do you think you would have the capacity to extend your PR with a change in tests/clients/test_pika.py, so it includes coverage for a BlockingConnection scenario?

[ghost]

Hi @Ferenc-,

I don't have much availability right now, and I'm not that comfortable with the unittest framework, but I will give it a try.

[ghost]

Sorry for the delay, had to take some time to look into pika implementation details. Let me know what you think about these changes.

[Ferenc-]

Sorry for the delay, had to take some time to look into pika implementation details. Let me know what you think about these changes.

Looks very good to me.
My only comment would have been the unused class attributes, that you have also fixed in the meantime, before I sent the comment.
So I am merging this now. Many thanks for the contribution.
If you have further improvements then feel free to open new PRs.