Update Travis configuration

.travis.yml

@@ -1,8 +1,11 @@
 os: osx
-osx_image: xcode9.3
+osx_image: xcode9.4
+before_install:
+  - brew update
+  - brew outdated swiftlint || brew upgrade swiftlint
 script:
   - xcodebuild -version
   - carthage version
   - swiftlint version
   - "./bootstrap.sh"
-  - set -o pipefail && env "NSUnbufferedIO=YES" xcodebuild test -scheme WWDC -project WWDC.xcodeproj | xcpretty -f `xcpretty-travis-formatter`
+  - set -o pipefail && env "NSUnbufferedIO=YES" xcodebuild test -scheme WWDC -project WWDC.xcodeproj | xcpretty -f `xcpretty-travis-formatter`

Brewfile

@@ -0,0 +1 @@
+brew "swiftlint"

WWDC/DownloadManager.swift

@@ -389,7 +389,7 @@ final class DownloadManager: NSObject {
         var notPresent = [String]()
 
         for session in expectedOnDisk {
-            if let asset = session.asset(ofType: SessionAssetType.hdVideo) {
+            if let asset = session.asset(ofType: .hdVideo) {
                 if !hasVideo(asset.remoteURL) {
                     notPresent.append(asset.relativeLocalURL)
                 }