swiftlint: command not found - how can I fix this?

[skydivedan]

My environment is CircleCI, just so you know. and this is running as a Mac executor.

My Dangerfile.swift file looks like this:

import Danger
let danger = Danger()

let editedFiles = danger.git.modifiedFiles + danger.git.createdFiles
message("These files have changed: \(editedFiles.joined(separator: ", "))")

SwiftLint.lint()

Now, while Danger does write in my PR about modified and created files, SwiftLint.lint() run, and gives this error:
/bin/sh: swiftlint: command not found

Why would that be? The "danger-swift" Package contains SwiftLint as a dependency, so wouldn't it be able to run SwiftLint? Do I need to actually install SwiftLint? If so, then what does the SwiftLint dependency do?

[skydivedan]

additionally, the docs say that when building my Package.swift file, I should add the the target like this:
.target(name: "eigen", dependencies: ["Danger"], path: "Artsy", sources: ["Stringify.swift"]),

Which I was unable to do exactly.... mine looks like this:
.target(name: "eigen", dependencies: [.product(name: "Danger", package: "swift")], path: "Artsy", sources: ["Stringify.swift"]),

When I do this, Package.resolved does not include Swiftlint. The result of Package.resolved behaves as if isDevelop is false -- which is weird considering that I can see that it's set to true right in the Package.swift file itself. So, I don't know why I'm seeing this behavior.