Cannot set session ID after the session has started. #5161
Description
I'm starting to receive this error after upgrading to 2.1 during tests. I've seen there are other tickets with this issue but they are old and closed.
I'm receiving the error for example with this code:
<?php
$client = static::createClient();
$crawler = $client->request('GET', '/contattaci/');
$this->assertTrue(200 === $client->getResponse()->getStatusCode());
// Fill in the form and submit it
$form = $crawler->selectButton('submit')->form(array(
'mp_contacttype[name]' => 'Test',
'mp_contacttype[email]' => 'test@test.com',
'mp_contacttype[phone]' => '34534534',
'mp_contacttype[message]' => 'Test',
));
$client->submit($form);The last client response is 500 error Cannot set session ID after the session has started. This test worked before. Has something changed?