Refs #34986 -- Fixed mocking in utils_tests.test_http.HttpDateProcessingTests.test_parsing_rfc850.

Mocking in the `datetime` module can be tricky. In CPython the datetime
C module is used, but PyPy uses a pure Python implementation. This
caused issues with the prior approach to mocking `datetime.datetime`.

See https://docs.python.org/3/library/unittest.mock-examples.html#partial-mocking

django/utils/http.py

@@ -1,8 +1,8 @@
 import base64
-import datetime
 import re
 import unicodedata
 from binascii import Error as BinasciiError
+from datetime import datetime, timezone
 from email.utils import formatdate
 from urllib.parse import quote, unquote
 from urllib.parse import urlencode as original_urlencode
@@ -113,10 +113,9 @@ def parse_http_date(date):
     else:
         raise ValueError("%r is not in a valid HTTP date format" % date)
     try:
-        tz = datetime.timezone.utc
         year = int(m["year"])
         if year < 100:
-            current_year = datetime.datetime.now(tz=tz).year
+            current_year = datetime.now(tz=timezone.utc).year
             current_century = current_year - (current_year % 100)
             if year - (current_year % 100) > 50:
                 # year that appears to be more than 50 years in the future are
@@ -129,7 +128,7 @@ def parse_http_date(date):
         hour = int(m["hour"])
         min = int(m["min"])
         sec = int(m["sec"])
-        result = datetime.datetime(year, month, day, hour, min, sec, tzinfo=tz)
+        result = datetime(year, month, day, hour, min, sec, tzinfo=timezone.utc)
         return int(result.timestamp())
     except Exception as exc:
         raise ValueError("%r is not a valid date" % date) from exc

tests/utils_tests/test_http.py

@@ -334,10 +334,9 @@ class HttpDateProcessingTests(unittest.TestCase):
         )
 
     @unittest.skipIf(platform.architecture()[0] == "32bit", "The Year 2038 problem.")
-    @mock.patch("django.utils.http.datetime.datetime")
+    @mock.patch("django.utils.http.datetime")
     def test_parsing_rfc850(self, mocked_datetime):
         mocked_datetime.side_effect = datetime
-        mocked_datetime.now = mock.Mock()
         now_1 = datetime(2019, 11, 6, 8, 49, 37, tzinfo=timezone.utc)
         now_2 = datetime(2020, 11, 6, 8, 49, 37, tzinfo=timezone.utc)
         now_3 = datetime(2048, 11, 6, 8, 49, 37, tzinfo=timezone.utc)