Run tests on bionic distribution & run AllTests with PHP 7.4 (#15720)

* run tests on php 7.4 / xenial

* composer update

* fix lfs check

* adjust travis.yml

* adds distribution param

* update submodule

* update travis.yml

* fix icon tests

* Fix array access error on PHP 7.4

* fix test

* avoid usage of deprecated assertArraySubset

* convert expectedException annotations

* avoid error on php 7.4

* Use assertion instead of conditional expection

* add separat expected test result asserialize output changed for PHP7.4

* updates expected ui files

* fix ui test

* run UI tests on xenial dist

* updates expected ui files

* Update core/DataTable/Renderer.php

* updates expected UI files

* submodule update

1 files changed, 1 insertions, 3 deletions

diff --git a/tests/PHPUnit/Framework/TestCase/SystemTestCase.php b/tests/PHPUnit/Framework/TestCase/SystemTestCase.php
index 1cc27afef4..a067283be7 100644
--- a/tests/PHPUnit/Framework/TestCase/SystemTestCase.php
+++ b/tests/PHPUnit/Framework/TestCase/SystemTestCase.php
@@ -461,9 +461,7 @@ abstract class SystemTestCase extends TestCase
                     ProcessedMetric::class,
                 ], true);
 
-                if ($unserialized === false) {
-                    throw new \Exception("Unknown serialization error.");
-                }
+                self::assertTrue($unserialized !== false, "Unknown serialization error.");
             } catch (\Exception $ex) {
                 $this->comparisonFailures[] = new \Exception("Processed response in '$processedFilePath' could not be unserialized: " . $ex->getMessage());
             }