The template engine is not constructed properly in install/index

1) phpbb_functional_acp_groups_test

Output found before DOCTYPE specification.

Failed asserting that '<br />

<font size='1'><table class='xdebug-error xe-catchable-fatal-error' dir='ltr' border='1' cellspacing='0' cellpadding='1'>

<tr><th align='left' bgcolor='#f57900' colspan="5"><span style='background-color: #cc0000; color: #fce94f; font-size: x-large;'>( ! )</span> Catchable fatal error: Argument 5 passed to phpbb\template\twig\twig::__construct() must be an instance of phpbb\template\twig\environment, none given, called in /home/travis/build/phpbb/phpbb/phpBB/install/index.php on line 271 and defined in /home/travis/build/phpbb/phpbb/phpBB/phpbb/template/twig/twig.php on line <i>86</i></th></tr>

<tr><th align='left' bgcolor='#e9b96e' colspan='5'>Call Stack</th></tr>

<tr><th align='center' bgcolor='#eeeeec'>#</th><th align='left' bgcolor='#eeeeec'>Time</th><th align='left' bgcolor='#eeeeec'>Memory</th><th align='left' bgcolor='#eeeeec'>Function</th><th align='left' bgcolor='#eeeeec'>Location</th></tr>

<tr><td bgcolor='#eeeeec' align='center'>1</td><td bgcolor='#eeeeec' align='center'>0.0031</td><td bgcolor='#eeeeec' align='right'>985456</td><td bgcolor='#eeeeec'>{main}( )</td><td title='/home/travis/build/phpbb/phpbb/phpBB/install/index.php' bgcolor='#eeeeec'>../index.php<b>:</b>0</td></tr>

<tr><td bgcolor='#eeeeec' align='center'>2</td><td bgcolor='#eeeeec' align='center'>0.8569</td><td bgcolor='#eeeeec' align='right'>16719136</td><td bgcolor='#eeeeec'>phpbb\template\twig\twig->__construct( )</td><td title='/home/travis/build/phpbb/phpbb/phpBB/install/index.php' bgcolor='#eeeeec'>../index.php<b>:</b>271</td></tr>

</table></font>' starts with "<!DOCTYPE".

/home/travis/build/phpbb/phpbb/tests/test_framework/phpbb_functional_test_case.php:852

/home/travis/build/phpbb/phpbb/tests/test_framework/phpbb_functional_test_case.php:137

/home/travis/build/phpbb/phpbb/tests/test_framework/phpbb_functional_test_case.php:297

/home/travis/build/phpbb/phpbb/tests/test_framework/phpbb_functional_test_case.php:62