Build Cloud Native Application section is tasks is throwing error while building image

[ddreggors]

Should there be a param for registry to push to or should there be more instructions here?

Issue
When following the TaskRun under 'Build Cloud Native Application' the following step fails:

tkn task start -n tektontutorial build-app \
  --inputresource='source=git-source' \
  --outputresource='builtImage=tekton-tutorial-greeter-image' \
  --param contextDir='springboot' \
  --showlog

It produces this error:

[push-image] error pushing image "example.com/rhdevelopers/tekton-tutorial-greeter" to "docker://example.com/rhdevelopers/tekton-tutorial-greeter": error copying layers and metadata from "containers-storage:[overlay@/var/lib/containers/storage+/run/containers/storage:overlay.imagestore=/var/lib/shared,overlay.mount_program=/usr/bin/fuse-overlayfs,overlay.mountopt=nodev,fsync=0]example.com/rhdevelopers/tekton-tutorial-greeter:latest" to "docker://example.com/rhdevelopers/tekton-tutorial-greeter:latest": Error trying to reuse blob sha256:4a2bc86056a8dfff6153b98fa9ff55b532584eb7b0d60aaf3ff7850a3df53fef at destination: error pinging docker registry example.com: invalid status code from registry 404 (Not Found)

To Reproduce
Steps to reproduce the behavior:

1. Run the RunTask command as desribed above
2. Watch log output on screen
3. After all the build image lines we see the push image lines and the error

Expected behavior
Command completes as described in tutorial. If a parameter is requires to change the url we are pushing to it should be mentioned to change this parameter.

Desktop (please complete the following information):

• OS: Fedora Linux
• Version: 33
• Browser: chrome - 90.0.4430.72 (Official Build) (64-bit)
• OpenShift Version:

   Client Version: 4.7.0
   Server Version: 4.7.0
   Kubernetes Version: v1.20.0+bd9e442
  

• Tekton Version :

   Client version: 0.15.0
   Pipeline version: v0.19.0
   Triggers version: v0.10.2