Index: wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php
===================================================================
--- wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php	(revision 39543)
+++ wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php	(working copy)
@@ -374,7 +374,7 @@
 			$parent = get_term( (int) $request['parent'], $this->taxonomy );
 
 			if ( ! $parent ) {
-				return new WP_Error( 'rest_term_invalid', __( "Parent term doesn't exist." ), array( 'status' => 400 ) );
+				return new WP_Error( 'rest_term_invalid', __( 'Parent term does not exist.' ), array( 'status' => 400 ) );
 			}
 		}
 
@@ -481,7 +481,7 @@
 			$parent = get_term( (int) $request['parent'], $this->taxonomy );
 
 			if ( ! $parent ) {
-				return new WP_Error( 'rest_term_invalid', __( "Parent term doesn't exist." ), array( 'status' => 400 ) );
+				return new WP_Error( 'rest_term_invalid', __( 'Parent term does not exist.' ), array( 'status' => 400 ) );
 			}
 		}