Stacktrace shows lines from updated file on disk, not code actually running

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-01-30.05:03:26.211>
labels = ['interpreter-core', 'type-feature', '3.8']
title = 'Stacktrace shows lines from updated file on disk, not code actually running'
updated_at = <Date 2019-01-31.06:16:57.533>
user = 'https://bugs.python.org/StevePryde'

bugs.python.org fields:

activity = <Date 2019-01-31.06:16:57.533>
actor = 'steven.daprano'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2019-01-30.05:03:26.211>
creator = 'Steve Pryde'
dependencies = []
files = []
hgrepos = []
issue_num = 35857
keywords = []
message_count = 11.0
messages = ['334544', '334550', '334551', '334552', '334553', '334554', '334555', '334579', '334589', '334590', '334608']
nosy_count = 5.0
nosy_names = ['scoder', 'steven.daprano', 'xtreak', 'jfine2358', 'Steve Pryde']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue35857'
versions = ['Python 3.8']