As of [this PR](https://github.com/apple/swift-corelibs-foundation/pull/2432) onto the Swift 5.1 branch, `XMLParser` lives in a split-off `FoundationXML` framework rather than `Foundation`. Once Swift 5.1 drops, perhaps we check against the compiler version to import accordingly? This is a reality as of [DEVELOPMENT-SNAPSHOT-2019-08-03-a](https://github.com/apple/swift/releases).