[spidermon] Fix subtract offset-naive and offset-aware (#439)

spidermon/contrib/scrapy/monitors/monitors.py

@@ -489,11 +489,16 @@ def test_execution_time(self):
         max_execution_time = crawler.settings.getint(SPIDERMON_MAX_EXECUTION_TIME)
         if not max_execution_time:
             return
-        now = datetime.datetime.utcnow()
+
         start_time = self.data.stats.get("start_time")
         if not start_time:
             return
 
+        if start_time.tzinfo:
+            now = self.utc_now_with_timezone()
+        else:
+            now = datetime.datetime.utcnow()
+
         duration = now - start_time
 
         msg = "The job has exceeded the maximum execution time"

spidermon/core/monitors.py

@@ -1,3 +1,4 @@
+from datetime import datetime, timezone
 from unittest import TestCase
 
 from spidermon import settings
@@ -101,6 +102,9 @@ def debug_tree(self, level=0):
     def _init_method(self):
         MonitorOptions.add_or_create(self.method.__func__)
 
+    def utc_now_with_timezone(self):
+        return datetime.utcnow().replace(tzinfo=timezone.utc)
+
     def __repr__(self):
         return "<MONITOR:({}) at {}>".format(self.name, hex(id(self)))