path issue for the locutus example with jsonnet renderer

[morvencao]

Found the follow issue while trying the locutus example with jsonnet renderer:

$ locutus --kubeconfig $KUBECONFIG --renderer=jsonnet --renderer.jsonnet.entrypoint=example/jsonnet/main.jsonnet --trigger=oneoff --render-only
level=info ts=2021-04-21T08:03:26.065791381Z caller=main.go:206 msg=running renderer=jsonnet trigger=oneoff
ts=2021-04-21T08:03:26.068048061Z caller=main.go:209 msg="Unhandled error received. Exiting..." err="failed to run trigger: failed to render: failed to evaluate: RUNTIME ERROR: couldn't open import \"rollout.json\": no match locally or in the Jsonnet library paths\n\texample/jsonnet/main.jsonnet:46:13-34\tobject <anonymous>\n\tDuring manifestation\t\n"

It is definitely path issue while importing rollout.json in example/jsonnet/main.jsonnet.

It works if we replace rollout.json with example/jsonnet/rollout.json, but it is not a good idea to use that relative path from CWD.