Inline MQTT paho imports

[balloob]

Description:

Some integrations rely optionally on MQTT (ie. OwnTracks, MySensors). These could no longer be imported because the MQTT imports would fail (mqtt is only an after_dependencies).

Related issue (if applicable): fixes #28464

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[probot-home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as its been labeled with a integration (mqtt) you are listed as a codeowner for? Thanks!

[frenck]

Maybe we should explicitly add # pylint: disable=import-outside-toplevel to those lines?

This gives us the hint it was meant intentionally and makes enabling the rule in the future much easier.

[MartinHjelmare]

We may need to move this line too:
https://github.com/home-assistant/home-assistant/blob/70e051e861b24ff293d625b50cd9bdd9d326fd69/homeassistant/components/mqtt/server.py#L7

[balloob]

Done & Done!

[balloob]

Done!

[pvizeli]

Not sure if the better fix is to install also after_dependencies requirements. On docker, we have also most packages preinstall without getting an issue.

Now the mqtt after_dependencies work, but we need to make a list which integration can be an after_dependencies and there is no warranty that we don't run into the same issue on integration with different after_dependencies.

This PR feels not like a real bug fix. I can't approve this PR.

[MartinHjelmare]

Yeah, it's not optimal.

[balloob]

We install after_dependencies during check config.

The camera integration has stream as an after_dependencies, which doesn't easily install on all operating systems.

I want to go ahead and merge this, so that OwnTracks and MySensors can be used again.

We can come up with a better solution in the future.