Add whatsnew

Author: mroeschke

doc/source/whatsnew/v0.21.0.txt

@@ -487,6 +487,7 @@ Conversion
 - Bug in ``IntervalIndex.is_non_overlapping_monotonic`` when intervals are closed on both sides and overlap at a point (:issue:`16560`)
 - Bug in :func:`Series.fillna` returns frame when ``inplace=True`` and ``value`` is dict (:issue:`16156`)
 - Bug in :attr:`Timestamp.weekday_name` returning a UTC-based weekday name when localized to a timezone (:issue:`17354`)
+- Bug in localization of a naive, datetime string in a ``Series`` constructor with a ``datetime[ns, timezone]`` dtype (:issue:`174151`)
 
 Indexing
 ^^^^^^^^