Add support for consumed generators in NormalizerFormatter, fixes #838

src/Monolog/Formatter/NormalizerFormatter.php

@@ -74,6 +74,10 @@ class NormalizerFormatter implements FormatterInterface
             $normalized = array();
 
             $count = 1;
+            if ($data instanceof \Generator && !$data->valid()) {
+                return array('...' => 'Generator is already consumed, aborting');
+            }
+
             foreach ($data as $key => $value) {
                 if ($count++ >= 1000) {
                     $normalized['...'] = 'Over 1000 items, aborting normalization';