Installation: unexpected HTTP status: 500 Internal Server Error

Symptom

kubectl logs -n kube-system image-manager-1 image-manager
time="2018-08-20T15:35:01Z" level=debug msg="main.main (main.go:34) Starting icp-image-manager ... "
time="2018-08-20T15:35:01Z" level=debug msg="main.main (main.go:57) Command line arguments: [/icp-image-manager serve --listen-address=0.0.0.0:8600 --private-key-path=/etc/icp-image-manager/tls.key --oidc-url=http://platform-identity-provider:4300 --registry-url=https://127.0.0.1:8500 --registry-server-name=vmh-lh-icp-master-prod.dcx.dlh.de:8500 --enable-https=true] "
time="2018-08-20T15:35:01Z" level=info msg="client.CreateApiserverClient (apiserverclient.go:70) Creating API server client for https://10.0.0.1:443 "
time="2018-08-20T15:35:01Z" level=info msg="main.serveAction (main.go:119) Starting to serve "
time="2018-08-20T15:48:01Z" level=info msg="authn.Anyauthenticator.Authenticate (any-authenticator.go:40) Failed to authenticate, error: Cannot authenticate by kubernetes "
time="2018-08-20T15:48:01Z" level=error msg="Failed to make token, error: unable to decode private key PEM: unable to get PrivateKey from PEM type: PRIVATE KEY"
time="2018-08-20T15:48:01Z" level=error msg="handler.AddRoutesHandlers.func1 (add-routes-handlers.go:41) Get token failed (GET /image-manager/api/v1/auth/token) "