Return error when failing to open log file

[finishes #133832779]

integration/groot/logging_test.go

@@ -140,6 +140,23 @@ var _ = Describe("Logging", func() {
 					Expect(string(allTheLogs)).To(ContainSubstring("\"log_level\":1"))
 				})
 			})
+
+			Context("and the log file cannot be created", func() {
+				It("returns an error to stdout", func() {
+					buffer := gbytes.NewBuffer()
+
+					_, err := Runner.
+						WithStdout(buffer).
+						WithLogFile("/path/to/log_file.log").
+						Create(groot.CreateSpec{
+							ID:        "my-image",
+							BaseImage: "/non/existent/rootfs",
+						})
+					Expect(err).To(HaveOccurred())
+
+					Expect(buffer).To(gbytes.Say("no such file or directory"))
+				})
+			})
 		})
 	})
 })

main.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"fmt"
 	"os"
 	"strings"
 
@@ -67,7 +66,10 @@ func main() {
 		cli.ErrWriter = os.Stdout
 
 		lagerLogLevel := translateLogLevel(logLevel)
-		logger, _ := configureLogger(lagerLogLevel, logFile)
+		logger, err := configureLogger(lagerLogLevel, logFile)
+		if err != nil {
+			return err
+		}
 		ctx.App.Metadata["logger"] = logger
 
 		configurer := store.NewConfigurer()
@@ -97,7 +99,7 @@ func configureLogger(logLevel lager.LogLevel, logFile string) (lager.Logger, err
 		var err error
 		logWriter, err = os.OpenFile(logFile, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644)
 		if err != nil {
-			return nil, fmt.Errorf("cannot create log file `%s`: %s", logFile, err)
+			return nil, err
 		}
 
 		if logLevel == lager.FATAL {