Environnement variables passed to proc_open() in https://github.com/symfony/symfony/blob/v3.4.2/src/Symfony/Component/Process/Process.php#L334 throw a ContextErrorException "Array to string conversion"

The reason seems to be that env vars are now always inherited v3.4.1...v3.4.2#diff-f9f2411040cda7b73402481facf3e4dd
but if a query string is present in the url then $env contains argv as an array

[
 "CONTENT_LENGTH" => "8610"
 "CONTENT_TYPE" => "application/x-www-form-urlencoded"
 "REQUEST_METHOD" => "POST"
 "QUERY_STRING" => "uniqid=s5a339da72130a"
 "argv" => [
          0 => "uniqid=s5a339da72130a" 
   ]
]

and apparently proc_open() does not expect a multi dimensionnal array for this parameter.