Use dumb solution that works even in Py2.7

Author: curusarn

logtail/frame.py

@@ -1,14 +1,16 @@
 # coding: utf-8
 from __future__ import print_function, unicode_literals
-from datetime import datetime, timezone
+from datetime import datetime
 
 from os import path
 import __main__
 
 def create_frame(record, message, context, include_extra_attributes=False):
     r = record.__dict__
     frame = {}
-    frame['dt'] = datetime.utcfromtimestamp(r['created']).replace(tzinfo=timezone.utc).isoformat()
+    # Python 3 only solution if we ever drop Python 2.7
+    # frame['dt'] = datetime.utcfromtimestamp(r['created']).replace(tzinfo=timezone.utc).isoformat()
+    frame['dt'] = "{}+00:00".format(datetime.utcfromtimestamp(r['created']).isoformat())
     frame['level'] = level = _levelname(r['levelname'])
     frame['severity'] = int(r['levelno'] / 10)
     frame['message'] = message