`tzinfo.fromutc()` fails when used for a fold-aware tzinfo implementation

GitHub fields:

assignee = 'https://github.com/abalkin'
closed_at = None
created_at = <Date 2016-11-03.18:55:50.016>
labels = ['type-feature', '3.8']
title = '`tzinfo.fromutc()` fails when used for a fold-aware tzinfo implementation'
updated_at = <Date 2018-06-05.18:37:55.782>
user = 'https://github.com/pganssle'

bugs.python.org fields:

activity = <Date 2018-06-05.18:37:55.782>
actor = 'belopolsky'
assignee = 'belopolsky'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2016-11-03.18:55:50.016>
creator = 'p-ganssle'
dependencies = []
files = []
hgrepos = []
issue_num = 28602
keywords = ['patch']
message_count = 10.0
messages = ['280007', '280009', '280011', '280012', '280014', '280015', '318743', '318772', '318773', '318780']
nosy_count = 3.0
nosy_names = ['tim.peters', 'belopolsky', 'p-ganssle']
pr_nums = ['7425']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue28602'
versions = ['Python 3.8']