cask: audit for minimal OS version in sparkle feeds

[SMillerDev]

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This should prevent situations where we forget to update the macOS dependency if there is a new version required upstream

[BrewTestBot]

Review period will end on 2022-11-01 at 00:00:00 UTC.

[Bo98]

Nice idea

[p-linnane]

Love this because it is often forgotten until something breaks.

[SMillerDev]

The recent iTerm update is exactly what motivated me here. If you have other things people forget, don't hesitate to ask me or make your own audit for it.

[BrewTestBot]

Review period ended.

[MikeMcQuaid]

Thanks @SMillerDev!

[Bo98]

LGTM

[Bo98]

Suggested change

	out, _, status = curl_output(cask.livecheck.url)
	out, _, status = curl_output("--fail", "--silent", "--location", cask.livecheck.url)

So that it will detect non-200 codes, follow redirects etc.

[Bo98]

Suggested change

	item = xml.get_elements("//rss//channel//item").first
	item = xml.elements["//rss//channel//item"]

Just for consistent code style with below. elements[...] should be the same as get_elements(...).first.

Doesn't really matter though.

[Bo98]

Suggested change

	min_os = item.elements["sparkle:minimumSystemVersion"].text
	min_os = item.elements["sparkle:minimumSystemVersion"]&.text

If there's no minimum version, then this will be nil.

[Bo98]

Suggested change

	min_os_string = OS::Mac::Version.new(min_os).strip_patch
	begin
	min_os_string = OS::Mac::Version.new(min_os).strip_patch
	rescue MacOSVersionError
	return
	end

In case the source returns an invalid macOS version, or one we don't support (e.g. Yosemite and earlier).

[MikeMcQuaid]

Oops sorry @Bo98!