Merge branch '6.4' into 7.3

* 6.4:
  [Validator] Skip tests using unavailable timezone on the local host
  [Yaml] Fix scope resolution operator in flow mapping keys

Author: nicolas-grekas

Tests/Constraints/TimezoneValidatorTest.php

@@ -270,6 +270,11 @@ public function testGroupedTimezonesWithInvalidCountry()
      */
     public function testDeprecatedTimezonesAreValidWithBC(string $timezone)
     {
+        // Skip test if the timezone is not available in the current timezone database
+        if (!\in_array($timezone, \DateTimeZone::listIdentifiers(\DateTimeZone::ALL_WITH_BC), true)) {
+            $this->markTestSkipped(sprintf('Timezone "%s" is not available in the current timezone database', $timezone));
+        }
+
         $constraint = new Timezone(\DateTimeZone::ALL_WITH_BC);
 
         $this->validator->validate($timezone, $constraint);