Add whatsnew

Author: mroeschke

doc/source/whatsnew/v0.21.0.txt

@@ -488,6 +488,7 @@ Conversion
 - 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 ``Timestamp.replace`` when replacing ``tzinfo`` around DST changes (:issue:`15683`)
+- Bug in localization of a naive, datetime string in a ``Series`` constructor with a ``datetime[ns, timezone]`` dtype (:issue:`174151`)
 
 Indexing
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