Simplify chart installable check
Simplify chart installable check

The error conveys at least as much information as the boolean.

Signed-off-by: Simon Alling <16999d1c3672a7ecf20a5e3805f080db6be9777a@gmail.com>

michelleN/deployment-manager,bacongobbler/helm,helm/helm,michelleN/deployment-manager,helm/helm,adamreese/helm,michelleN/deployment-manager,adamreese/helm,michelleN/deployment-manager,bacongobbler/helm