Add intl-version to matrix

As it looks like some intl-versions are bolloks....

.github/workflows/actions.yml

@@ -40,19 +40,20 @@ jobs:
       matrix:
         # operating-system: [ubuntu-latest, windows-latest, macos-latest]
         php-versions: ['7.3', '7.4', '8.0', '8.1', '8.2']
+        icu-versions: ['73.1', '71.1', '69.1', '67.1']
         experimental: [false]
         include:
           - php-versions: '8.3'
             experimental: true
-    name: PHP ${{ matrix.php-versions }} # Test on ${{ matrix.operating-system }}
+    name: PHP ${{ matrix.php-versions }}-icu${{ matrix.icu-versions }} # Test on ${{ matrix.operating-system }}
     steps:
       - name: Checkout
         uses: actions/checkout@v2
       - name: Setup PHP
         uses: shivammathur/setup-php@v2
         with:
           php-version: ${{ matrix.php-versions }}
-          extensions: sodium
+          extensions: sodium, intl-${{matrix.icu-version}}
           ini-values: post_max_size=256M, short_open_tag=On
           coverage: xdebug
       - name: prepare

src/CalendarDayFactory.php

@@ -34,7 +34,6 @@
 
 use IntlCalendar;
 use Org_Heigl\Holidaychecker\Exceptions\UnknownCalendar;
-use UnexpectedValueException;
 use function sprintf;
 
 class CalendarDayFactory
@@ -47,11 +46,14 @@ public static function createCalendarDay(int $day, int $month, string $calendar)
 				$calendar
 			));
 		}
-		$calendar = IntlCalendar::createInstance('UTC', '@calendar=' . $calendar);
-		if (null === $calendar) {
-			throw new UnexpectedValueException('Expected instance of IntlCalendar, got null');
-		}
+		$icuCalendar = IntlCalendar::createInstance('UTC', '@calendar=' . $calendar);
 
-		return new CalendarDay($day, $month, $calendar);
+		if ($icuCalendar === null) {
+			throw new UnknownCalendar(sprintf(
+				'The %s calendar could not be created',
+				$calendar
+			));
+		}
+		return new CalendarDay($day, $month, $icuCalendar);
 	}
 }