Tensorflow получает результат скрипта Python с именем Stack Overflow

Я пытаюсь запустить команду из PHP:

<?php

$msg = exec("python /var/tensorflow/tensorflow/examples/label_image/label_image.py --graph=/tmp/output_graph.pb --labels=/tmp/output_labels.txt --input_layer=Mul --output_layer=final_result --image=/var/www/ruze.jpg",$msg2,$retval);

var_dump($msg);
var_dump($msg2);
var_dump($retval);

?>

Результат:

string(0) "" array(0) { } int(1)

Он отлично работает в терминале:

root@sp:~# python /var/tensorflow/tensorflow/examples/label_image/label_image.py --graph=/tmp/output_graph.pb --labels=/tmp/output_labels.txt --input_layer=Mul --output_layer=final_result --image=/var/www/ruze.jpg
2018-04-09 17:25:45.196419: I tensorflow/core/platform/cpu_feature_guard.cc:140] Your CPU supports instructions that this TensorFlow binary was not compiled to use: AVX2 FMA
2018-04-09 17:25:45.416509: W tensorflow/core/framework/op_def_util.cc:343] Op BatchNormWithGlobalNormalization is deprecated. It will cease to work in GraphDef version 9. Use tf.nn.batch_normalization().
roses 0.99905473

tulips 0.00085386337
sunflowers 8.967988e-05
dandelion 1.0716676e-06
daisy 5.9500644e-07

Я использую Debian 9.4