Docs on lockfile creation are outdated

[lmbarros]

Our Update Locking docs provide some code snippets to show users how to create lockfiles correctly in some languages. I found that at least two of these snippets are outdated.

The shell snippet uses lockfile, which AFAICT was part of procmail, which is unmaintained for a long time. I am not sure what would be the modern replacement. Maybe the utilities in the lockfile-progs package -- though it doesn't seem to be available for Alpine Linux, so I am not sure it is a good choice.

The Python snipped still uses Python 2 syntax, and is based on a library that appears to be deprecated. I am not a Python connoisseur, but I did some tests (using the newer filelock library) and this looks like the modern equivalent:

from filelock import FileLock

lock = FileLock("/tmp/balena/updates.lock")
with lock:
    print(lock.lock_file, 'is locked.')

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[vipulgupta2048]

@cywang117 @kb2ma @pipex I understand lockfile and its creation are under the domain of the supervisor. Can we make improvements to these examples mentioned in this issue to provide updated information for our users.