Added test for DateTimeField validation when server has timezone with DST and…

Added test for DateTimeField validation when server has timezone with DST and input is a native time in a DST shift interval.
Added pytz to requirements-testing.txt to reproduce the case.

requirements/requirements-testing.txt

@@ -2,3 +2,4 @@
 pytest==3.0.5
 pytest-django==3.1.2
 pytest-cov==2.4.0
+pytz==2016.10

tests/test_fields.py

@@ -9,7 +9,7 @@ import pytest
 from django.http import QueryDict
 from django.test import TestCase, override_settings
 from django.utils import six
-from django.utils.timezone import utc
+from django.utils.timezone import utc, pytz
 
 import rest_framework
 from rest_framework import serializers
@@ -1205,6 +1205,23 @@ class TestNaiveDateTimeField(FieldValues):
     field = serializers.DateTimeField(default_timezone=None)
 
 
+class TestNaiveDayLightSavingTimeTimeZoneDateTimeField(FieldValues):
+    """
+    Invalid values for `DateTimeField` with datetime in DST shift (non-existing or ambiguous) and timezone with DST.
+    Timezone America/New_York has DST shift from 2017-03-12T02:00:00 to 2017-03-12T03:00:00 and
+     from 2017-11-05T02:00:00 to 2017-11-05T01:00:00 in 2017.
+    """
+    valid_inputs = {}
+    invalid_inputs = {
+        '2017-03-12T02:30:00': [
+            'Datetime can not be converted to server timezone due to NonExistentTimeError.'],
+        '2017-11-05T01:30:00': [
+            'Datetime can not be converted to server timezone due to AmbiguousTimeError.']
+    }
+    outputs = {}
+    field = serializers.DateTimeField(default_timezone=pytz.timezone('America/New_York'))
+
+
 class TestTimeField(FieldValues):
     """
     Valid and invalid values for `TimeField`.