bpo-22005: Fixed unpickling instances of datetime classes pickled by Python 2. (GH-11017)

encoding='latin1' should be used for successful decoding.
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index 78b123f..2f838c4 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -38,6 +38,7 @@
 import _strptime
 #
 
+pickle_loads = {pickle.loads, pickle._loads}
 
 pickle_choices = [(pickle, pickle, proto)
                   for proto in range(pickle.HIGHEST_PROTOCOL + 1)]
@@ -1434,6 +1435,19 @@
             self.assertEqual(orig, derived)
         self.assertEqual(orig.__reduce__(), orig.__reduce_ex__(2))
 
+    def test_compat_unpickle(self):
+        tests = [
+            b"cdatetime\ndate\n(S'\\x07\\xdf\\x0b\\x1b'\ntR.",
+            b'cdatetime\ndate\n(U\x04\x07\xdf\x0b\x1btR.',
+            b'\x80\x02cdatetime\ndate\nU\x04\x07\xdf\x0b\x1b\x85R.',
+        ]
+        args = 2015, 11, 27
+        expected = self.theclass(*args)
+        for data in tests:
+            for loads in pickle_loads:
+                derived = loads(data, encoding='latin1')
+                self.assertEqual(derived, expected)
+
     def test_compare(self):
         t1 = self.theclass(2, 3, 4)
         t2 = self.theclass(2, 3, 4)
@@ -2098,6 +2112,24 @@
             derived = unpickler.loads(green)
             self.assertEqual(orig, derived)
 
+    def test_compat_unpickle(self):
+        tests = [
+            b'cdatetime\ndatetime\n('
+            b"S'\\x07\\xdf\\x0b\\x1b\\x14;\\x01\\x00\\x10\\x00'\ntR.",
+
+            b'cdatetime\ndatetime\n('
+            b'U\n\x07\xdf\x0b\x1b\x14;\x01\x00\x10\x00tR.',
+
+            b'\x80\x02cdatetime\ndatetime\n'
+            b'U\n\x07\xdf\x0b\x1b\x14;\x01\x00\x10\x00\x85R.',
+        ]
+        args = 2015, 11, 27, 20, 59, 1, 64**2
+        expected = self.theclass(*args)
+        for data in tests:
+            for loads in pickle_loads:
+                derived = loads(data, encoding='latin1')
+                self.assertEqual(derived, expected)
+
     def test_more_compare(self):
         # The test_compare() inherited from TestDate covers the error cases.
         # We just want to test lexicographic ordering on the members datetime
@@ -3069,6 +3101,19 @@
             derived = unpickler.loads(green)
             self.assertEqual(orig, derived)
 
+    def test_compat_unpickle(self):
+        tests = [
+            b"cdatetime\ntime\n(S'\\x14;\\x10\\x00\\x10\\x00'\ntR.",
+            b'cdatetime\ntime\n(U\x06\x14;\x10\x00\x10\x00tR.',
+            b'\x80\x02cdatetime\ntime\nU\x06\x14;\x10\x00\x10\x00\x85R.',
+        ]
+        args = 20, 59, 16, 64**2
+        expected = self.theclass(*args)
+        for data in tests:
+            for loads in pickle_loads:
+                derived = loads(data, encoding='latin1')
+                self.assertEqual(derived, expected)
+
     def test_bool(self):
         # time is always True.
         cls = self.theclass
@@ -3441,6 +3486,40 @@
             self.assertEqual(derived.tzname(), 'cookie')
         self.assertEqual(orig.__reduce__(), orig.__reduce_ex__(2))
 
+    def test_compat_unpickle(self):
+        tests = [
+            b"cdatetime\ntime\n(S'\\x05\\x06\\x07\\x01\\xe2@'\n"
+            b"ctest.datetimetester\nPicklableFixedOffset\n(tR"
+            b"(dS'_FixedOffset__offset'\ncdatetime\ntimedelta\n"
+            b"(I-1\nI68400\nI0\ntRs"
+            b"S'_FixedOffset__dstoffset'\nNs"
+            b"S'_FixedOffset__name'\nS'cookie'\nsbtR.",
+
+            b'cdatetime\ntime\n(U\x06\x05\x06\x07\x01\xe2@'
+            b'ctest.datetimetester\nPicklableFixedOffset\n)R'
+            b'}(U\x14_FixedOffset__offsetcdatetime\ntimedelta\n'
+            b'(J\xff\xff\xff\xffJ0\x0b\x01\x00K\x00tR'
+            b'U\x17_FixedOffset__dstoffsetN'
+            b'U\x12_FixedOffset__nameU\x06cookieubtR.',
+
+            b'\x80\x02cdatetime\ntime\nU\x06\x05\x06\x07\x01\xe2@'
+            b'ctest.datetimetester\nPicklableFixedOffset\n)R'
+            b'}(U\x14_FixedOffset__offsetcdatetime\ntimedelta\n'
+            b'J\xff\xff\xff\xffJ0\x0b\x01\x00K\x00\x87R'
+            b'U\x17_FixedOffset__dstoffsetN'
+            b'U\x12_FixedOffset__nameU\x06cookieub\x86R.',
+        ]
+
+        tinfo = PicklableFixedOffset(-300, 'cookie')
+        expected = self.theclass(5, 6, 7, 123456, tzinfo=tinfo)
+        for data in tests:
+            for loads in pickle_loads:
+                derived = loads(data, encoding='latin1')
+                self.assertEqual(derived, expected, repr(data))
+                self.assertIsInstance(derived.tzinfo, PicklableFixedOffset)
+                self.assertEqual(derived.utcoffset(), timedelta(minutes=-300))
+                self.assertEqual(derived.tzname(), 'cookie')
+
     def test_more_bool(self):
         # time is always True.
         cls = self.theclass
@@ -3789,6 +3868,43 @@
             self.assertEqual(derived.tzname(), 'cookie')
         self.assertEqual(orig.__reduce__(), orig.__reduce_ex__(2))
 
+    def test_compat_unpickle(self):
+        tests = [
+            b'cdatetime\ndatetime\n'
+            b"(S'\\x07\\xdf\\x0b\\x1b\\x14;\\x01\\x01\\xe2@'\n"
+            b'ctest.datetimetester\nPicklableFixedOffset\n(tR'
+            b"(dS'_FixedOffset__offset'\ncdatetime\ntimedelta\n"
+            b'(I-1\nI68400\nI0\ntRs'
+            b"S'_FixedOffset__dstoffset'\nNs"
+            b"S'_FixedOffset__name'\nS'cookie'\nsbtR.",
+
+            b'cdatetime\ndatetime\n'
+            b'(U\n\x07\xdf\x0b\x1b\x14;\x01\x01\xe2@'
+            b'ctest.datetimetester\nPicklableFixedOffset\n)R'
+            b'}(U\x14_FixedOffset__offsetcdatetime\ntimedelta\n'
+            b'(J\xff\xff\xff\xffJ0\x0b\x01\x00K\x00tR'
+            b'U\x17_FixedOffset__dstoffsetN'
+            b'U\x12_FixedOffset__nameU\x06cookieubtR.',
+
+            b'\x80\x02cdatetime\ndatetime\n'
+            b'U\n\x07\xdf\x0b\x1b\x14;\x01\x01\xe2@'
+            b'ctest.datetimetester\nPicklableFixedOffset\n)R'
+            b'}(U\x14_FixedOffset__offsetcdatetime\ntimedelta\n'
+            b'J\xff\xff\xff\xffJ0\x0b\x01\x00K\x00\x87R'
+            b'U\x17_FixedOffset__dstoffsetN'
+            b'U\x12_FixedOffset__nameU\x06cookieub\x86R.',
+        ]
+        args = 2015, 11, 27, 20, 59, 1, 123456
+        tinfo = PicklableFixedOffset(-300, 'cookie')
+        expected = self.theclass(*args, **{'tzinfo': tinfo})
+        for data in tests:
+            for loads in pickle_loads:
+                derived = loads(data, encoding='latin1')
+                self.assertEqual(derived, expected)
+                self.assertIsInstance(derived.tzinfo, PicklableFixedOffset)
+                self.assertEqual(derived.utcoffset(), timedelta(minutes=-300))
+                self.assertEqual(derived.tzname(), 'cookie')
+
     def test_extreme_hashes(self):
         # If an attempt is made to hash these via subtracting the offset
         # then hashing a datetime object, OverflowError results.  The