reverted:
--- b/core/modules/system/src/Tests/Module/InstallUninstallTest.php
+++ a/core/modules/system/src/Tests/Module/InstallUninstallTest.php
@@ -133,7 +133,7 @@
       // appropriate messages appear in the logs.
       foreach ($modules_to_install as $module_to_install) {
         $this->assertText(t('hook_modules_installed fired for @module', array('@module' => $module_to_install)));
+        $this->assertLogMessage('system', "%module module installed.", array('%module' => $module_to_install), RfcLogLevel::INFO);
-        $this->assertLogMessage('modules', "%module module installed.", array('%module' => $module_to_install), RfcLogLevel::INFO);
         $this->assertInstallModuleUpdates($module_to_install);
         $this->assertModuleSuccessfullyInstalled($module_to_install);
       }
@@ -255,7 +255,7 @@
     // module was just uninstalled, since the {watchdog} table won't be there
     // anymore.)
     $this->assertText(t('hook_modules_uninstalled fired for @module', array('@module' => $module)));
+    $this->assertLogMessage('system', "%module module uninstalled.", array('%module' => $module), RfcLogLevel::INFO);
-    $this->assertLogMessage('modules', "%module module uninstalled.", array('%module' => $module), RfcLogLevel::INFO);
 
     // Check that the module's database tables no longer exist.
     $this->assertModuleTablesDoNotExist($module);