Improve logging

[yuvipanda]

The logging here is mostly print statements. It should instead move to using the self.log object in the Configurable. And output in appropriate levels (debug, info and exception)

Definition of done

• Move all functions into the class so they can use self.log
• Print output of xfs_* to self.error if return code is 0, else print only to debug stream.
• No more print statements left
• Make choices that reduce overall number of log lines printed

[yuvipanda]

The current volume of logs is also causing big increases in cloud logging costs.

[agoose77]

From digging around, my understanding is that the cause of the high volume of logs in GCP is that the setup_project call (see https://git.launchpad.net/ubuntu/+source/xfsprogs/tree/quota/project.c?h=ubuntu/plucky#n192) is noisily complaining about special files.

@yuvipanda addressed this by releasing a development version of jupyterhub-home-nfs with a patch that, amongst other things, moves the setup call inside a stricter guard that only runs for changed quotas. This means that we will see far fewer instances of log messages like this.

We still need to address the fact that changing quotas is noisy, but it looks like some of this issue is already implicitly addressed.

[yuvipanda]

@agoose77 i don't think my PR addresses that specifically - that was mostly done for error handling purposes. If that also addressed some of the logging stuff that's great!

I do think logging needs to be clearer here so debugging can be better, so keep an eye on that too.

Tagging @sunu here as well :)