engine, lang: Fix simple test failures

Two bugs sneaked in while pushing old stuff.

engine/resources/docker_container.go

@@ -402,7 +402,7 @@ func (obj *DockerContainerRes) Cmp(r engine.Res) error {
 		return fmt.Errorf("the APIVersion differs")
 	}
 	if obj.Force != res.Force {
-		return fmt.Errorf("The Force field differs")
+		return fmt.Errorf("the Force field differs")
 	}
 	return nil
 }

lang/funcs/core/deploy/readfile_func.go

@@ -135,7 +135,7 @@ func (obj *ReadFileFunc) Stream() error {
 			// We could use it directly, but it feels like less correct.
 			//content, err := obj.data.Fs.ReadFile(path) // open the remote file system
 			if err != nil {
-				return errwrap.Wrapf(err, "can't read file `%s` (%s)", obj.filename, path)
+				return errwrap.Wrapf(err, "can't read file `%s` (%s)", *obj.filename, path)
 			}
 
 			result := string(content) // convert to string