Add defensive checks to prevent inscrutable error messages #6623

Job	Run time
Deploy (bundler, bundler)	13s
Deploy (cargo, cargo)	12s
Deploy (composer, composer)	10s
Deploy (docker, docker)	11s
Deploy (elm, elm)	18s
Deploy (git_submodules, gitsubmodule)	11s
Deploy (github_actions, github-actions)	17s
Deploy (go_modules, gomod)	9s
Deploy (gradle, gradle)	8s
Deploy (hex, mix)	9s
Deploy (maven, maven)	14s
Deploy (npm_and_yarn, npm)	9s
Deploy (nuget, nuget)	10s
Deploy (pub, pub)	8s
Deploy (python, pip)	13s
Deploy (swift, swift)	8s
Deploy (terraform, terraform)	12s
	3m 12s

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