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>>> from datetime import datetime, timezone
 >>> dt = datetime.now(timezone.utc)
 >>> fmt = '%Y-%m-%d %H:%M:%S.%f %Z%z'
 >>> datetime.strptime(dt.strftime(fmt), fmt)
 Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/cpython/Lib/_strptime.py", line 500, in _strptime_datetime
 tt, fraction = _strptime(data_string, format)
 File "/cpython/Lib/_strptime.py", line 337, in _strptime
 (data_string, format))
 ValueError: time data '2014-08-21 11:29:13.537251 UTC+00:00+0000'
 does not match format '%Y-%m-%d %H:%M:%S.%f %Z%z'
The issue is that dt.strftime('%Z') produces 'UTC+00:00'
(due to timezone.utc.tzname(dt) returning 'UTC+00:00')
instead of 'UTC' that strptime() accepts and %Z examples [1]
in the docs demonstrate.
[1] https://docs.python.org/3.4/library/datetime.html#strftime-and-strptime-behavior