message: gitops-plugin: add meaningful error message for the cluster listing page
diff: @@ -28,16 +28,21 @@ import {
  } from '@backstage/core';
  import ClusterTable from '../ClusterTable/ClusterTable';
  -import { Button, Typography } from '@material-ui/core';
  +import { Button } from '@material-ui/core';
  import { useAsync, useLocalStorage } from 'react-use';
  import { gitOpsApiRef, ListClusterStatusesResponse } from '../../api';
  +import { Alert } from '@material-ui/lab';
  const ClusterList: FC<{}> = () => {
  const [loginInfo] = useLocalStorage<{
  token: string;
  username: string;
  name: string;
  - }>('githubLoginDetails');
  + }>('githubLoginDetails', {
  + token: '',
  + username: '',
  + name: 'Guest',
  + });
  const api = useApi(gitOpsApiRef);
  @@ -59,9 +64,19 @@ const ClusterList: FC<{}> = () => {
  } else if (error) {
  content = (
  <Content>
  - <Typography variant="h4" color="error">
  - Failed to load cluster, {String(error)}
  - </Typography>
  + <div>
  + <Alert severity="error">
  + Error encountered while fetching list of GitOps-managed cluster.{' '}
  + {error.toString()}
  + </Alert>
  + <Alert severity="info">
  + Please make sure that you start GitOps-API backend on localhost port
  + 3008 before using this plugin.
  + </Alert>
  + <Alert severity="info">
  + If you're Guest, please login via GitHub first.
  + </Alert>
  + </div>
  </Content>
  );
  } else {
  