debos: Improve error messages

Rework the error handling to show where an error occured during the run.
Also print all error messages to the log rather than stdout.

Signed-off-by: Christopher Obbard <chris.obbard@collabora.com>

cmd/debos/debos.go

@@ -163,7 +163,7 @@ func main() {
  // attempt to create a fakemachine
  m, err = fakemachine.NewMachineWithBackend(options.Backend)
  if err != nil {
- log.Printf("error creating fakemachine: %v", err)
+ log.Printf("Couldn't create fakemachine: %v", err)
 
  /* fallback to running on the host unless the user has chosen
  * a specific backend */
@@ -253,7 +253,7 @@ func main() {
  }
  memsize, err := units.RAMInBytes(options.Memory)
  if err != nil {
- fmt.Printf("Couldn't parse memory size: %v\n", err)
+ log.Printf("Couldn't parse memory size: %v\n", err)
  context.State = debos.Failed
  return
  }
@@ -268,7 +268,7 @@ func main() {
  if options.ScratchSize != "" {
  size, err := units.FromHumanSize(options.ScratchSize)
  if err != nil {
- fmt.Printf("Couldn't parse scratch size: %v\n", err)
+ log.Printf("Couldn't parse scratch size: %v\n", err)
  context.State = debos.Failed
  return
  }
@@ -318,12 +318,13 @@ func main() {
 
  exitcode, err := m.RunInMachineWithArgs(args)
  if err != nil {
- fmt.Println(err)
+ log.Printf("Couldn't start fakemachine: %v\n", err)
  context.State = debos.Failed
  return
  }
 
  if exitcode != 0 {
+ log.Printf("fakemachine failed with non-zero exitcode: %d\n", exitcode)
  context.State = debos.Failed
  return
  }
@@ -355,6 +356,7 @@ func main() {
  if _, err = os.Stat(context.Rootdir); os.IsNotExist(err) {
  err = os.Mkdir(context.Rootdir, 0755)
  if err != nil && os.IsNotExist(err) {
+ log.Printf("Couldn't create rootdir: %v\n", err)
  context.State = debos.Failed
  return
  }