Highlight false positives in check-sqs-messages when metric is unsupported

[majormoses]

Pull Request Checklist

#380

General

• Update Changelog following the conventions laid out here

• Update README with any necessary configuration snippets

• Binstubs are created if needed

• RuboCop passes

• Existing tests pass

Purpose

Highlight false positives in check-sqs-messages when metric is unsupported

Previously you could see something like this:

bundle _1.17.3_ exec ./bin/check-sqs-messages.rb -r us-east-1 -q test-sensu-380 -m ApproximateAgeOfOldestMessage -c 1
NEWER VERSION AVAILABLE: Please upgrade to AWS SDK For Ruby V3
SQSMsgs OK: 0 messages in test-sensu-380 queue

Instead this will now properly notify responders to the (now) known bug. As it appears to be an api limitation and not something we did in our code we will keep the discussion open for a proper solution but first things first is getting it to tell the truth. After the fix it should look something like this:

bundle exec ./bin/check-sqs-messages.rb -r us-east-1 -q test-sensu-380 -m ApproximateAgeOfOldestMessage -c 1
SQSMsgs UNKNOWN: failed to pull metric ApproximateAgeOfOldestMessage on queue: test-sensu-380.
available attributes: {"QueueArn"=>"arn:aws:sqs:us-east-1:REDACTED:test-sensu-380", "ApproximateNumberOfMessages"=>"2", "ApproximateNumberOfMessagesNotVisible"=>"0", "ApproximateNumberOfMessagesDelayed"=>"0", "CreatedTimestamp"=>"1592356301", "LastModifiedTimestamp"=>"1592356301", "VisibilityTimeout"=>"30", "MaximumMessageSize"=>"262144", "MessageRetentionPeriod"=>"345600", "DelaySeconds"=>"0", "ReceiveMessageWaitTimeSeconds"=>"0"}

Signed-off-by: Ben Abrams me@benabrams.it

Known Compatibility Issues

There is a bug that is being masked, this surfaces it. This will not actually break any code, system, etc but deploying this will result in several unknowns from community members.