Added pytz exception in compat module.

Mock pytz.timezone localize in tests.
Ref: #4986

requirements/requirements-testing.txt

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

rest_framework/compat.py

@@ -275,6 +275,14 @@ except ImportError:
     def pygments_css(style):
         return None
 
+
+try:
+    import pytz
+    from pytz.exceptions import InvalidTimeError
+except ImportError:
+    InvalidTimeError = Exception
+
+
 # `separators` argument to `json.dumps()` differs between 2.x and 3.x
 # See: http://bugs.python.org/issue22767
 if six.PY3:
@@ -339,6 +347,7 @@ def set_many(instance, field, value):
         field = getattr(instance, field)
         field.set(value)
 
+
 def include(module, namespace=None, app_name=None):
     from django.conf.urls import include
     if django.VERSION < (1,9):

rest_framework/fields.py

@@ -33,7 +33,8 @@ from django.utils.translation import ugettext_lazy as _
 
 from rest_framework import ISO_8601
 from rest_framework.compat import (
-    get_remote_field, unicode_repr, unicode_to_repr, value_from_object
+    InvalidTimeError, get_remote_field, unicode_repr, unicode_to_repr,
+    value_from_object
 )
 from rest_framework.exceptions import ErrorDetail, ValidationError
 from rest_framework.settings import api_settings
@@ -1108,7 +1109,7 @@ class DateTimeField(Field):
         if (field_timezone is not None) and not timezone.is_aware(value):
             try:
                 return timezone.make_aware(value, field_timezone)
-            except Exception:
+            except InvalidTimeError:
                 self.fail('make_aware', timezone=field_timezone)
         elif (field_timezone is None) and timezone.is_aware(value):
             return timezone.make_naive(value, utc)

tests/test_fields.py

@@ -9,10 +9,10 @@ import pytest
 from django.http import QueryDict
 from django.test import TestCase, override_settings
 from django.utils import six
-from django.utils.timezone import pytz, utc
+from django.utils.timezone import utc
 
 import rest_framework
-from rest_framework import serializers
+from rest_framework import compat, serializers
 from rest_framework.fields import is_simple_callable
 
 try:
@@ -1217,7 +1217,16 @@ class TestNaiveDayLightSavingTimeTimeZoneDateTimeField(FieldValues):
         '2017-11-05T01:30:00': ['Invalid datetime for the timezone "America/New_York".']
     }
     outputs = {}
-    field = serializers.DateTimeField(default_timezone=pytz.timezone('America/New_York'))
+
+    class MockTimezone:
+        @staticmethod
+        def localize(value, is_dst):
+            raise compat.InvalidTimeError()
+
+        def __str__(self):
+            return 'America/New_York'
+
+    field = serializers.DateTimeField(default_timezone=MockTimezone())
 
 
 class TestTimeField(FieldValues):