remove dependency on pytz (encode#8984)

* remove pytz

* Revert "remove pytz"

This reverts commit 393609d.

* remove pytz, more subtly

Author: Mathieu Dupuy

rest_framework/fields.py

@@ -29,7 +29,11 @@
 from django.utils.formats import localize_input, sanitize_separators
 from django.utils.ipv6 import clean_ipv6_address
 from django.utils.translation import gettext_lazy as _
-from pytz.exceptions import InvalidTimeError
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
 
 from rest_framework import ISO_8601
 from rest_framework.exceptions import ErrorDetail, ValidationError
@@ -1148,8 +1152,10 @@ def enforce_timezone(self, value):
                 if not valid_datetime(dt):
                     self.fail('make_aware', timezone=field_timezone)
                 return dt
-            except InvalidTimeError:
-                self.fail('make_aware', timezone=field_timezone)
+            except Exception as e:
+                if pytz and isinstance(e, pytz.exceptions.InvalidTimeError):
+                    self.fail('make_aware', timezone=field_timezone)
+                raise e
         elif (field_timezone is None) and timezone.is_aware(value):
             return timezone.make_naive(value, datetime.timezone.utc)
         return value

setup.py

@@ -83,7 +83,7 @@ def get_version(package):
     author_email='[email protected]',  # SEE NOTE BELOW (*)
     packages=find_packages(exclude=['tests*']),
     include_package_data=True,
-    install_requires=["django>=3.0", "pytz", 'backports.zoneinfo;python_version<"3.9"'],
+    install_requires=["django>=3.0", 'backports.zoneinfo;python_version<"3.9"'],
     python_requires=">=3.6",
     zip_safe=False,
     classifiers=[

tests/test_fields.py

@@ -9,7 +9,12 @@
 from unittest.mock import patch
 
 import pytest
-import pytz
+
+try:
+    import pytz
+except ImportError:
+    pytz = None
+
 from django.core.exceptions import ValidationError as DjangoValidationError
 from django.db.models import IntegerChoices, TextChoices
 from django.http import QueryDict
@@ -1604,15 +1609,16 @@ class TestPytzNaiveDayLightSavingTimeTimeZoneDateTimeField(FieldValues):
     }
     outputs = {}
 
-    class MockTimezone(pytz.BaseTzInfo):
-        @staticmethod
-        def localize(value, is_dst):
-            raise pytz.InvalidTimeError()
+    if pytz:
+        class MockTimezone(pytz.BaseTzInfo):
+            @staticmethod
+            def localize(value, is_dst):
+                raise pytz.InvalidTimeError()
 
-        def __str__(self):
-            return 'America/New_York'
+            def __str__(self):
+                return 'America/New_York'
 
-    field = serializers.DateTimeField(default_timezone=MockTimezone())
+        field = serializers.DateTimeField(default_timezone=MockTimezone())
 
 
 @patch('rest_framework.utils.timezone.datetime_ambiguous', return_value=True)