Docker image points to old garethr/kubernetes-json-schema repo

[orrc]

Using the current-latest garethr/kubeval Docker image (at the moment 0.14.0) doesn't work with newer schemas from instrumenta/kubernetes-json-schema.

From what I gather from #135, that is the "official" Docker image for kubeval.

Based on garethr/kubernetes-json-schema#26, and from finding https://kubernetesjsonschema.dev/ in the source, it appears that instrumenta/kubernetes-json-schema should be the place to read schemas from.

For example, using the v1.15.7 schema doesn't currently work:

$ docker run --rm -t -v `pwd`:`pwd`:ro -w `pwd` garethr/kubeval:0.14.0 \
    --strict -v 1.15.7 *.yml

1 error occurred:

* Problem loading schema from the network at 
https://raw.githubusercontent.com/garethr/kubernetes-json-schema/master/v1.15.7-standalone-strict/deployment.json: 
Could not read schema from HTTP, response status is 404 Not Found

[orrc]

From instrumenta/kubernetes-json-schema#11 (comment), a workaround to this issue (and kubernetesjsonschema.dev being outdated) is to add the -s parameter with the GitHub raw URL: 👍

$ docker run --rm -t -v `pwd`:`pwd`:ro -w `pwd` garethr/kubeval:0.14.0 \
    -s https://raw.githubusercontent.com/instrumenta/kubernetes-json-schema/master/ \
    --strict -v 1.15.7 *.yml