Failure in non-existent chart retrival should be graceful

[varditn]

Expected Behaviour

If one of the Dependencies charts cannot be fetched, Armador should fail gracefully upon retrieval failure and log out a clear message , for example Chart cannot be found

Actual Behaviour

when configuring a chart to pull that doesn't exist (ie: stable/nonexist), the processHelm() and helm.Fetch() error out well, but chartList.processCharts() doesn't catch the error, and attempts other things that pollute the log messaging.

Initial error:

ERROR	commands/cmd.go:87 An error occured in the command: exit status 1 with string Error: chart "nonexist" matching version "" not found in stable index. (try 'helm repo update'). no chart name found

followed by an unneeded warning, but ok:

WARN	armador/chart.go:44	Unable to fetch and extract nonexist: cmd: Run failed with Error: chart "nonexist" matching version "" not found in stable index. (try 'helm repo update'). no chart name found

but then it continues with:

WARN	armador/chartList.go:78	chart: nonexist and path:  will be processed
DEBUG	commands/cmd.go:62	running command	{"name": "helm-dep-up", "dir": "", "command": "helm dep update"}
ERROR	commands/cmd.go:87	An error occured in the command: exit status 1 with string Error: chart metadata (Chart.yaml) missing

Steps to Reproduce

1. set one of the chart under prereqCharts, additionalValues or dependencies to a non-existant chart (ie: stable/nonexist)
2. run armador create