Fix for Python 3.6 test_mute_duration

tests/integration/models/reddit/test_modmail.py

@@ -1,3 +1,4 @@
+import sys
 from datetime import datetime
 from unittest import mock
 
@@ -42,9 +43,19 @@ def test_mute_duration(self, _):
             conversation.mute(7)
             conversation = self.reddit.subreddit("all").modmail("g46rw")
             assert conversation.user.mute_status["isMuted"]
-            diff = datetime.fromisoformat(
-                conversation.user.mute_status["endDate"]
-            ) - datetime.fromisoformat(conversation.mod_actions[-1].date)
+            if sys.version_info >= (3, 7, 0):
+                diff = datetime.fromisoformat(
+                    conversation.user.mute_status["endDate"]
+                ) - datetime.fromisoformat(conversation.mod_actions[-1].date)
+            else:
+                end_date = "".join(
+                    conversation.user.mute_status["endDate"].rsplit(":", 1)
+                )
+                start_date = "".join(conversation.mod_actions[-1].date.rsplit(":", 1))
+                date_format = "%Y-%m-%dT%H:%M:%S.%f%z"
+                diff = datetime.strptime(end_date, date_format) - datetime.strptime(
+                    start_date, date_format
+                )
             assert diff.days == 6  # 6 here because it is not 7 whole days
 
     @mock.patch("time.sleep", return_value=None)