Add hint to missing dependency message

Signed-off-by: Johannes Hertenstein <git@j6s.dev>

cmd/helm/install.go

@@ -214,6 +214,7 @@ func runInstall(args []string, client *action.Install, valueOpts *values.Options
 		// As of Helm 2.4.0, this is treated as a stopping condition:
 		// https://github.com/helm/helm/issues/2209
 		if err := action.CheckDependencies(chartRequested, req); err != nil {
+			err = errors.Wrap(err, "An error occurred while checking for chart dependencies. You may need to run `helm dependency build` to fetch missing dependencies")
 			if client.DependencyUpdate {
 				man := &downloader.Manager{
 					Out:              out,

cmd/helm/testdata/output/upgrade-with-missing-dependencies.txt

@@ -1 +1 @@
-Error: found in Chart.yaml, but missing in charts/ directory: reqsubchart2
+Error: An error occurred while checking for chart dependencies. You may need to run `helm dependency build` to fetch missing dependencies: found in Chart.yaml, but missing in charts/ directory: reqsubchart2

cmd/helm/upgrade.go

@@ -146,6 +146,7 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 			}
 			if req := ch.Metadata.Dependencies; req != nil {
 				if err := action.CheckDependencies(ch, req); err != nil {
+					err = errors.Wrap(err, "An error occurred while checking for chart dependencies. You may need to run `helm dependency build` to fetch missing dependencies")
 					if client.DependencyUpdate {
 						man := &downloader.Manager{
 							Out:              out,