minor verify-goimports tweak + document future improvements
minor verify-goimports tweak + document future improvements

checks args for a better error message, and writes informational
messages to stderr

Signed-off-by: Ashley Davis <2a98ad09b55d7402451cbad533f334a828c02124@jetstack.io>

jetstack/cert-manager,jetstack/cert-manager,cert-manager/cert-manager,cert-manager/cert-manager,cert-manager/cert-manager,jetstack/cert-manager