Cleanup config load error handling

Signed-off-by: Daniel Nephin <dnephin@docker.com>

cli/config/config.go

@@ -75,18 +75,18 @@ func Load(configDir string) (*configfile.ConfigFile, error) {
 	if _, err := os.Stat(filename); err == nil {
 		file, err := os.Open(filename)
 		if err != nil {
-			return configFile, errors.Errorf("%s - %v", filename, err)
+			return configFile, errors.Wrap(err, filename)
 		}
 		defer file.Close()
 		err = configFile.LoadFromReader(file)
 		if err != nil {
-			err = errors.Errorf("%s - %v", filename, err)
+			err = errors.Wrap(err, filename)
 		}
 		return configFile, err
 	} else if !os.IsNotExist(err) {
 		// if file is there but we can't stat it for any reason other
 		// than it doesn't exist then stop
-		return configFile, errors.Errorf("%s - %v", filename, err)
+		return configFile, errors.Wrap(err, filename)
 	}
 
 	// Can't find latest config file so check for the old one
@@ -96,12 +96,12 @@ func Load(configDir string) (*configfile.ConfigFile, error) {
 	}
 	file, err := os.Open(confFile)
 	if err != nil {
-		return configFile, errors.Errorf("%s - %v", confFile, err)
+		return configFile, errors.Wrap(err, confFile)
 	}
 	defer file.Close()
 	err = configFile.LegacyLoadFromReader(file)
 	if err != nil {
-		return configFile, errors.Errorf("%s - %v", confFile, err)
+		return configFile, errors.Wrap(err, confFile)
 	}
 	return configFile, nil
 }

cli/config/config_test.go

@@ -2,6 +2,7 @@ package config
 
 import (
 	"bytes"
+	"io"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -13,6 +14,7 @@ import (
 	"github.com/docker/docker/pkg/homedir"
 	"github.com/gotestyourself/gotestyourself/assert"
 	is "github.com/gotestyourself/gotestyourself/assert/cmp"
+	"github.com/pkg/errors"
 )
 
 func setupConfigDir(t *testing.T) (string, func()) {
@@ -77,7 +79,8 @@ func TestEmptyFile(t *testing.T) {
 	assert.NilError(t, err)
 
 	_, err = Load(tmpHome)
-	assert.ErrorContains(t, err, "EOF")
+	assert.Equal(t, errors.Cause(err), io.EOF)
+	assert.ErrorContains(t, err, ConfigFileName)
 }
 
 func TestEmptyJSON(t *testing.T) {