print error messages in error boundary component

src/components/UI/ErrorBoundary/ErrorBoundary.js

@@ -1,35 +1,36 @@
 import PropTypes from 'prop-types';
 import React from 'react';
 
-const ErrorComponent = () => {
-  const issueUrl = "https://github.com/netlify/netlify-cms/issues/new";
-  return (
-    <div className="nc-errorBoundary">
-      <h1 className="nc-errorBoundary-heading">Sorry!</h1>
-      <p>
-        <span>There's been an error - please </span>
-        <a href={issueUrl} target="_blank" className="nc-errorBoundary-link">report it</a>!
-      </p>
-    </div>
-  );
+const DefaultErrorComponent = () => {
 };
 
-export class ErrorBoundary extends React.Component {
-  static propTypes = {
-    render: PropTypes.element,
-  };
+const ISSUE_URL = "https://github.com/netlify/netlify-cms/issues/new";
 
+export class ErrorBoundary extends React.Component {
   state = {
     hasError: false,
+    errorMessage: '',
   };
 
   componentDidCatch(error) {
     console.error(error);
-    this.setState({ hasError: true });
+    this.setState({ hasError: true, errorMessage: error.toString() });
   }
 
   render() {
-    const errorComponent = this.props.errorComponent || <ErrorComponent/>;
-    return this.state.hasError ? errorComponent : this.props.children;
+    const { hasError, errorMessage } = this.state;
+    if (!hasError) {
+      return this.props.children;
+    }
+    return (
+      <div className="nc-errorBoundary">
+        <h1 className="nc-errorBoundary-heading">Sorry!</h1>
+        <p>
+          <span>There's been an error - please </span>
+          <a href={ISSUE_URL} target="_blank" className="nc-errorBoundary-link">report it</a>!
+        </p>
+        <p>{errorMessage}</p>
+      </div>
+    );
   }
 }