Image tools missing raises exception

[roleyfoley]

Expected Behaviour

When docker cannot be accessed to pull a required docker image the generation process should fail and return an exception

Current Behaviour

When working with docker image pulls if a docker command cannot be found during an pregeneration script a warning is logged in the script but the process continues

Possible Solution

This was before the introduction of the HAMLET_SKIP_IMAGE_PULL env var which was added to work around scenarios where you are testing deployment generation offline and don't want the image skipped. The soft fail was an attempt to work around this, the env var configuration is more explicit and ensures that its acknowledged by users that the pull failed

Context