Issue #3285230 by xjm, benjifisher, phenaproxima, mikelutz, quietone:...

    $this->assertCount(1, $messages);

    $message = reset($messages);

    // Assert critical parts of the error message, but not the exact message,

    // since it depends on Guzzle's internal implementation of PSR-7.

    $id = $migration->getPluginId();

    $this->assertEquals("$id:uri:download: Client error: `GET $invalid_url` resulted in a `404 Not Found` response ($invalid_url)", $message->message);

    $this->assertStringContainsString("$id:uri:download:", $message->message);

    $this->assertStringContainsString($invalid_url, $message->message);

    $this->assertEquals(MigrationInterface::MESSAGE_ERROR, $message->level);

    // Check that the second row was migrated successfully.

              $html_output = 'Called from ' . $caller['function'] . ' line ' . $caller['line'];

              $html_output .= '<hr />' . $request->getMethod() . ' request to: ' . $request->getUri();

              // Get the response body as a string. Any errors are silenced as

              // tests should not fail if there is a problem. On PHP 7.4

              // \Drupal\Tests\migrate\Functional\process\DownloadFunctionalTest

              // fails without the usage of a silence operator.

              $body = @(string) $response->getBody();

              /* $var \Psr\Http\Message\StreamInterface $stream */

              $stream = $response->getBody();

              // Get the response body as a string.

              $body = $stream->isReadable()

                ? (string) $stream

                : 'Response is not readable.';

              // On redirect responses (status code starting with '3') we need

              // to remove the meta tag that would do a browser refresh. We

              // don't want to redirect developers away when they look at the