Fix linting issues

.travis.yml

@@ -1,11 +1,17 @@
 language: go
 
+go:
+  - stable
+
 before_install:
   - curl https://raw.githubusercontent.com/golang/dep/master/install.sh | sh
+  - go get -u github.com/alecthomas/gometalinter
+  - gometalinter --install
 
 install:
   - dep ensure
 
 script:
+  - make lint
   - make test
   - make

internal/app/s3manager/errors.go

@@ -20,8 +20,8 @@ const (
 
 // Errors that may be returned from an S3 client.
 var (
-	ErrBucketDoesNotExist = errors.New("The specified bucket does not exist.")
-	ErrKeyDoesNotExist    = errors.New("The specified key does not exist.")
+	ErrBucketDoesNotExist = errors.New("The specified bucket does not exist.") // nolint: golint
+	ErrKeyDoesNotExist    = errors.New("The specified key does not exist.")    // nolint: golint
 )
 
 // handleHTTPError handles HTTP errors.