Hooks should fail on missing dependencies

[wingsofovnia]

Currently, if dependencies (e.g. goimports or gofumpt) are missing, the hooks do not report valid error code to pre-commit and it fails silently, which is only detected if --verbose is passed.

> pre-commit run --all-files --show-diff-on-failure --verbose
...
go import/fmt............................................................Passed
- hook id: go-fmt-import
- duration: 0s

/home/vsts/work/1/pre-commit-cache/repok815yl26/run-go-fmt-import.sh: 3: goimports: not found

/home/vsts/work/1/pre-commit-cache/repok815yl26/run-go-fmt-import.sh: 3: goimports: not found

gofumpt..................................................................Passed
- hook id: gofumpt
- duration: 0s

/home/vsts/work/1/pre-commit-cache/repok815yl26/run-go-gofumpt.sh: 3: gofumpt: not found

/home/vsts/work/1/pre-commit-cache/repok815yl26/run-go-gofumpt.sh: 3: gofumpt: not found

As you can see, pre-commit reports Passed although the hook failed.