Fix tests and whatnew notes

Author: mroeschke

doc/source/whatsnew/v0.21.0.txt

@@ -303,7 +303,7 @@ length 2+ levels, so a :class:`MultiIndex` is always returned from all of the
 UTC Localization with Series
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-Previously, :func:`to_datetime` did not localize datetime ``Series`` data when ``utc=True`` was passed. Now, :func:`to_datetime` will correctly localize `Series` with a `datetime64[ns, UTC]` data type to be consistent with how list-like and Index data are handled. (:issue:`6415`).
+Previously, :func:`to_datetime` did not localize datetime ``Series`` data when ``utc=True`` was passed. Now, :func:`to_datetime` will correctly localize ``Series`` with a ``datetime64[ns, UTC]`` dtype to be consistent with how list-like and `Index` data are handled. (:issue:`6415`).
 
   Previous Behavior
 

pandas/io/sql.py

@@ -821,13 +821,9 @@ def _harmonize_columns(self, parse_dates=None):
 
                 if (col_type is datetime or col_type is date or
                         col_type is DatetimeTZDtype):
-                    if col_type is DatetimeTZDtype:
-                        # Convert tz-aware Datetime SQL columns to UTC
-                        self.frame[col_name] = _handle_date_column(df_col,
-                                                                   utc=True)
-                    else:
-                        self.frame[col_name] = _handle_date_column(df_col)
-
+                    # Convert tz-aware Datetime SQL columns to UTC
+                    utc = col_type is DatetimeTZDtype
+                    self.frame[col_name] = _handle_date_column(df_col, utc=utc)
                 elif col_type is float:
                     # floats support NA, can always convert!
                     self.frame[col_name] = df_col.astype(col_type, copy=False)

pandas/tests/indexes/datetimes/test_tools.py

@@ -292,17 +292,20 @@ def test_to_datetime_utc_true_with_series_single_value(self):
         expected = pd.Series([pd.Timestamp(ts, tz='utc')])
         tm.assert_series_equal(result, expected)
 
-    @pytest.mark.parametrize("data, dtype",
-                             [('2013-01-01 00:00:00-01:00', None),
-                              ('2013-01-01 00:00:00-01:00', 'datetime64[ns]'),
-                              ('2013-01-01 01:00:00', None),
-                              ('2013-01-01 01:00:00', 'datetime64[ns]')])
-    def test_to_datetime_utc_true_with_naive_dtype_series(self, data, dtype):
-        test_dates = [data] * 10
-        ser = pd.Series(test_dates, dtype=dtype)
-        result = pd.to_datetime(ser, utc=True)
-        expected_data = [pd.Timestamp('20130101 01:00:00', tz='utc')] * 10
-        expected = pd.Series(expected_data)
+    def test_to_datetime_utc_true_with_series_tzaware_string(self):
+        ts = '2013-01-01 00:00:00-01:00'
+        expected_ts = '2013-01-01 01:00:00'
+        data = pd.Series([ts] * 3)
+        result = pd.to_datetime(data, utc=True)
+        expected = pd.Series([pd.Timestamp(expected_ts, tz='utc')] * 3)
+        tm.assert_series_equal(result, expected)
+
+    @pytest.mark.parametrize('date, dtype',
+                             [('2013-01-01 01:00:00', 'datetime64[ns]'),
+                              ('2013-01-01 01:00:00', 'datetime64[ns, UTC]')])
+    def test_to_datetime_utc_true_with_series_datetime_ns(self, date, dtype):
+        expected = pd.Series([pd.Timestamp('2013-01-01 01:00:00', tz='UTC')])
+        result = pd.to_datetime(pd.Series([date], dtype=dtype), utc=True)
         tm.assert_series_equal(result, expected)
 
     def test_to_datetime_tz_psycopg2(self):

pandas/tests/io/test_sql.py

@@ -1314,7 +1314,6 @@ def check(col):
         expected = sql.read_sql_table("types_test_data", self.conn)
         col = expected.DateColWithTz
         assert is_datetime64tz_dtype(col.dtype)
-        # Removed ".astype('datetime64[ns, UTC]')"after GH 6415 was fixed
         tm.assert_series_equal(df.DateColWithTz, expected.DateColWithTz)
 
         # xref #7139

pandas/tests/test_multilevel.py

@@ -2137,7 +2137,6 @@ def test_set_index_datetime(self):
                           '2011-07-19 08:00:00', '2011-07-19 09:00:00'],
              'value': range(6)})
         df.index = pd.to_datetime(df.pop('datetime'), utc=True)
-        # Removed 'tz_localize('utc') below after GH 6415 was fixed
         df.index = df.index.tz_convert('US/Pacific')
 
         expected = pd.DatetimeIndex(['2011-07-19 07:00:00',