Fixed templates for YAML unit tests

Author: ezimuel

util/template/test/allowed-warnings

@@ -1,10 +1,10 @@
         // check for allowed_warnings
-        $headers = $this->client->transport->getLastConnection()->getLastRequestInfo()['response']['headers'];
-        if (isset($headers['Warning'])) {
+        $warning = $response->getHeaderLine('Warning');
+        if (!empty($warning)) {
             $expectedHeaders = :expected;
             $contains = false;
             foreach ($expectedHeaders as $expected) {
-                $contains = $contains || (false !== strpos($headers['Warning'][0], $expected));
+                $contains = $contains || (false !== strpos($warning, $expected));
             }
             $this->assertTrue($contains);
         }

util/template/test/warnings

@@ -1,7 +1,7 @@
         // check for warnings
-        $headers = $this->client->transport->getLastConnection()->getLastRequestInfo()['response']['headers'];
-        $this->assertTrue(isset($headers['Warning']));
+        $warning = $response->getHeader('Warning');
+        $this->assertNotEmpty($warning);
         $expectedHeaders = :expected;
         foreach ($expectedHeaders as $expected) {
-            $this->assertStringContainsString($expected, implode('', $headers['Warning']));
+            $this->assertStringContainsString($expected, implode('', $warning));
         }