list and exec on non-existent or inaccessible services fails silently on S3 KMS backend

[nick96]

I'm running into an issue when running chamber list or chamber exec with a service that doesn't exist will report back in the same way as if the list was empty. I found this out when I accidentally messed up the IAM policy to allow an EC2 instance to read the secrets for a particular chamber service. The instance didn't have access to the service it needed but successfully running exec, just not setting any of the secrets as env vars. I see similar behavior with list, where the table is just empty.

I'm not sure if there is a way of differentiating non-existent, empty and inaccessible, from stepping through with a debugger I can see that the list objects response for a non-existent service is empty:

github.com/aws/aws-sdk-go/aws/request.Pagination {
	NewRequest: github.com/aws/aws-sdk-go/service/s3.(*S3).ListObjectsPagesWithContext.func1,
	EndPageOnSameToken: false,
	started: true,
	prevTokens: []interface {} len: 0, cap: 0, nil,
	nextTokens: []interface {} len: 0, cap: 0, nil,
	err: error nil,
	curPage: interface {}(*github.com/aws/aws-sdk-go/service/s3.ListObjectsOutput) *{
		_: struct {} {},
		CommonPrefixes: []*github.com/aws/aws-sdk-go/service/s3.CommonPrefix len: 0, cap: 0, nil,
		Contents: []*github.com/aws/aws-sdk-go/service/s3.Object len: 0, cap: 0, nil,
		Delimiter: *string nil,
		EncodingType: *string nil,
		IsTruncated: *false,
		Marker: *"",
		MaxKeys: *1000,
		Name: *"chamber-bucket",
		NextMarker: *string nil,
		Prefix: *"non-existant-app/__kms",},}

Perhaps we could write a warning that would simplify the debugging process?