*feature*

>Warning: A component is `contentEditable` and contains `children` managed by React. It is now your responsibility to guarantee that none of those nodes are unexpectedly modified or duplicated. This is probably not intentional.

It would help heaps if I would know _which_ component is causing this.
render() {
          return <table>{this.props.children}</table>;
        }
      }
      class FancyTable extends React.Component {
        render() {
          return <Table>{this.props.children}</Table>;
        }
      }
      function Viz1() {
        return <table><FancyRow /></table>;
      }
      function App1() {
        return <Viz1 />;
      }
      ReactTestUtils.renderIntoDocument(<App1 />);
      expectDev(console.error.calls.count()).toBe(1);
      expectDev(
        normalizeCodeLocInfo(console.error.calls.argsFor(0)[0]),
      ).toContain(
        '\n    in tr (at **)' +
          '\n    in Row (at **)' +
          '\n    in FancyRow (at **)' +
          '\n    in table (at **)' +
          '\n    in Viz1 (at **)',
      );
      function Viz2() {