Use convenience function for testing tz object

For all of these tests, the most important part of the test is ensuring
that the correct tzinfo object was attached, so it makes sense to add a
convenience function that asserts that they are identical *and* have the
same tzinfo object.

dateutil/test/test_parser.py

@@ -348,17 +348,21 @@ def test_parse_bytearray(self):
 
 
 class TestTzinfoInputTypes(object):
+    def assert_equal_same_tz(self, dt1, dt2):
+        assert dt1 == dt2
+        assert dt1.tzinfo is dt2.tzinfo
+
     def test_tzinfo_dict_could_return_none(self):
         dstr = "2017-02-03 12:40 BRST"
         result = parse(dstr, tzinfos={"BRST": None})
         expected = datetime(2017, 2, 3, 12, 40)
-        assert result == expected
+        self.assert_equal_same_tz(result, expected)
 
     def test_tzinfos_callable_could_return_none(self):
         dstr = "2017-02-03 12:40 BRST"
         result = parse(dstr, tzinfos=lambda *args: None)
         expected = datetime(2017, 2, 3, 12, 40)
-        assert result == expected
+        self.assert_equal_same_tz(result, expected)
 
     def test_invalid_tzinfo_input(self):
         dstr = "2014 January 19 09:00 UTC"
@@ -372,15 +376,14 @@ def test_valid_tzinfo_tzinfo_input(self):
         tzinfos = {"UTC": tz.UTC}
         expected = datetime(2014, 1, 19, 9, tzinfo=tz.UTC)
         res = parse(dstr, tzinfos=tzinfos)
-        assert res == expected
-        assert res.tzinfo is expected.tzinfo
+        self.assert_equal_same_tz(res, expected)
 
     def test_valid_tzinfo_unicode_input(self):
         dstr = "2014 January 19 09:00 UTC"
         tzinfos = {u"UTC": u"UTC+0"}
-        expected = datetime(2014, 1, 19, 9, tzinfo=tz.UTC)
+        expected = datetime(2014, 1, 19, 9, tzinfo=tz.tzstr("UTC+0"))
         res = parse(dstr, tzinfos=tzinfos)
-        assert res == expected
+        self.assert_equal_same_tz(res, expected)
 
     def test_valid_tzinfo_callable_input(self):
         dstr = "2014 January 19 09:00 UTC"
@@ -390,8 +393,7 @@ def tzinfos(*args, **kwargs):
 
         expected = datetime(2014, 1, 19, 9, tzinfo=tz.tzstr("UTC+0"))
         res = parse(dstr, tzinfos=tzinfos)
-        assert res == expected
-        assert res.tzinfo is expected.tzinfo
+        self.assert_equal_same_tz(res, expected)
 
 
 class ParserTest(unittest.TestCase):