modules: Fix "hugo mod get -u" with no arguments

Fixes #6826
Closes #6825

commands/commandeer.go

@@ -20,8 +20,6 @@ import (
 
 	"golang.org/x/sync/semaphore"
 
-	"github.com/gohugoio/hugo/modules"
-
 	"io/ioutil"
 
 	"github.com/gohugoio/hugo/common/herrors"
@@ -312,14 +310,8 @@ func (c *commandeer) loadConfig(mustHaveConfigFile, running bool) error {
 		doWithCommandeer,
 		doWithConfig)
 
-	if err != nil {
-		if mustHaveConfigFile {
-			return err
-		}
-		if err != hugolib.ErrNoConfigFile && !modules.IsNotExist(err) {
-			return err
-		}
-
+	if err != nil && mustHaveConfigFile {
+		return err
 	} else if mustHaveConfigFile && len(configFiles) == 0 {
 		return hugolib.ErrNoConfigFile
 	}

commands/mod.go

@@ -77,6 +77,7 @@ Run "go help get" for more information. All flags available for "go get" is also
 ` + commonUsage,
 			RunE: func(cmd *cobra.Command, args []string) error {
 				return c.withModsClient(false, func(c *modules.Client) error {
+
 					// We currently just pass on the flags we get to Go and
 					// need to do the flag handling manually.
 					if len(args) == 1 && args[0] == "-h" {