Description:
------------
DateTime::createFromFormat(), DateTimeImmutable::createFromFormat() and date_create_from_format() fail to create a DateTime(Immutable) object when the format is RFC3339_EXTENDED and a valid date string is supplied but using the constructors / date_create() works.

See https://3v4l.org/shJD7

Test script:
---------------
<?php
$datestring = '2017-06-03T00:08:10.881UTC';

if ($date = DateTime::createFromFormat(DateTime::RFC3339_EXTENDED, $datestring)) {
    print_r($date);
} else {
    print_r(DateTime::getLastErrors());
}

if ($date = new DateTime($datestring)) {
    print_r($date);
} else {
    print_r(DateTime::getLastErrors());
}


Expected result:
----------------
DateTime Object
(
    [date] => 2017-06-03 00:08:10.881000
    [timezone_type] => 3
    [timezone] => UTC
)
DateTime Object
(
    [date] => 2017-06-03 00:08:10.881000
    [timezone_type] => 3
    [timezone] => UTC
)

Actual result:
--------------
Array
(
    [warning_count] => 0
    [warnings] => Array
        (
        )

    [error_count] => 2
    [errors] => Array
        (
            [20] => The format separator does not match
            [21] => The timezone could not be found in the database
        )

)
DateTime Object
(
    [date] => 2017-06-03 00:08:10.881000
    [timezone_type] => 3
    [timezone] => UTC
)