Fix gopass update writable check (gopasspw#1838)

Fixes gopasspw#1837

RELEASE_NOTES=[BUGFIX] Fix gopass update

Signed-off-by: Dominik Schulz <dominik.schulz@gauner.org>

internal/action/errors.go

@@ -54,8 +54,9 @@ const (
 
 // ExitError returns a user friendly CLI error
 func ExitError(exitCode int, err error, format string, args ...interface{}) error {
+	msg := fmt.Sprintf(format, args...)
 	if err != nil {
-		debug.Log("Stacktrace: %+v", err)
+		debug.Log("%s - stacktrace: %+v", err)
 	}
-	return cli.Exit(fmt.Sprintf(format, args...), exitCode)
+	return cli.Exit(msg, exitCode)
 }

internal/updater/access_others.go

@@ -0,0 +1,9 @@
+// +build !windows
+
+package updater
+
+import "golang.org/x/sys/unix"
+
+func canWrite(path string) error {
+	return unix.Access(path, unix.W_OK)
+}

internal/updater/access_windows.go

@@ -0,0 +1,7 @@
+// +build windows
+
+package updater
+
+func canWrite(path string) error {
+	return nil
+}

internal/updater/updateable.go

@@ -50,18 +50,6 @@ func IsUpdateable(ctx context.Context) error {
 	return nil
 }
 
-func canWrite(path string) error {
-	// check if we can write to this file. we open it for writing in
-	// append mode to not truncate it and immediately close the filehandle since
-	// we're only interested in the error.
-	fh, err := os.OpenFile(path, os.O_WRONLY|os.O_APPEND, 0755)
-	if e := fh.Close(); err != nil {
-		return e
-	}
-
-	return err
-}
-
 var executable = func(ctx context.Context) (string, error) {
 	path, err := os.Executable()
 	if err != nil {