diff -u b/core/modules/mysql/mysql.install b/core/modules/mysql/mysql.install
--- b/core/modules/mysql/mysql.install
+++ b/core/modules/mysql/mysql.install
@@ -46,11 +46,11 @@
         }
       }
 
-      $tables_missing_key_text = 'For this to work properly all tables should have a primary key. The following table(s) do no have a primary key: '. implode(', ', $tables_missing_key);
+      $tables_missing_key_text = 'For this to work properly all tables should have a primary key. The following table(s) do no have a primary key: ' . implode(', ', $tables_missing_key);
 
       if ($isolation_level == 'READ-COMMITTED' && $missing_primary_key) {
         $severity_level = REQUIREMENT_ERROR;
-        $description = 'This site is using the database transaction level "READ COMMITTED". '. $tables_missing_key_text;
+        $description = 'This site is using the database transaction level "READ COMMITTED". ' . $tables_missing_key_text;
       }
       elseif ($isolation_level == 'REPEATABLE-READ') {
         $severity_level = REQUIREMENT_WARNING;
@@ -61,14 +61,14 @@
       }
       elseif ($isolation_level == 'READ-UNCOMMITTED' || $isolation_level == 'SERIALIZED') {
         $severity_level = REQUIREMENT_ERROR;
-        $description = 'This site is using the database transaction level "'.$isolation_level. '". This database transaction level is not supported by Drupal. The recommended database transaction level for Drupal is "READ COMMITTED".';
+        $description = 'This site is using the database transaction level "' . $isolation_level . '". This database transaction level is not supported by Drupal. The recommended database transaction level for Drupal is "READ COMMITTED".';
       }
 
       $requirements['mysql_transaction_level'] = [
         'title' => t('Database Isolation Level'),
         'severity' => $severity_level,
         'value' => $isolation_level,
-        'description' => t($description. ' See the <a href=":performance_doc">setting MySQL transaction isolation level</a> page for more information.', [
+        'description' => t($description . ' See the <a href=":performance_doc">setting MySQL transaction isolation level</a> page for more information.', [
           ':performance_doc' => 'https://www.drupal.org/docs/system-requirements/setting-the-mysql-transaction-isolation-level',
         ]),
       ];
diff -u b/core/modules/mysql/tests/src/Functional/RequirementsTest.php b/core/modules/mysql/tests/src/Functional/RequirementsTest.php
--- b/core/modules/mysql/tests/src/Functional/RequirementsTest.php
+++ b/core/modules/mysql/tests/src/Functional/RequirementsTest.php
@@ -57,7 +57,7 @@
     $this->assertCount(1, $elements);
     $this->assertStringStartsWith('REPEATABLE-READ', $elements[0]->getParent()->getText());
     // Ensure it is a warning.
-    $this->assertStringContainsString('warning', $elements[0]->getParent()->getParent()->find('css', 'summary')->getAttribute('class'));    // Set the isolation level to a level that produces a warning.
+    $this->assertStringContainsString('warning', $elements[0]->getParent()->getParent()->find('css', 'summary')->getAttribute('class'));
 
     // Rollback the isolation level to read committed.
     $this->writeIsolationLevelSettings('READ COMMITTED');
@@ -94,7 +94,7 @@
     $this->assertCount(1, $elements);
     $this->assertStringStartsWith('REPEATABLE-READ', $elements[0]->getParent()->getText());
     // Ensure it is a warning.
-    $this->assertStringContainsString('warning', $elements[0]->getParent()->getParent()->find('css', 'summary')->getAttribute('class'));    // Set the isolation level to a level that produces a warning.
+    $this->assertStringContainsString('warning', $elements[0]->getParent()->getParent()->find('css', 'summary')->getAttribute('class'));
 
     // Rollback the isolation level to read committed.
     $this->writeIsolationLevelSettings('READ COMMITTED');
@@ -106,7 +106,7 @@
     ]);
     $this->assertCount(1, $elements);
     $this->assertStringStartsWith('READ-COMMITTED', $elements[0]->getParent()->getText());
-    // Ensure it is a not a warning.
+    // Ensure it is an error.
     $this->assertStringContainsString('error', $elements[0]->getParent()->getParent()->find('css', 'summary')->getAttribute('class'));
   }