ensurepip and pip install failures on macOS Sierra with non-system Python 2.7.x

GitHub fields:

assignee = 'https://github.com/ned-deily'
closed_at = None
created_at = <Date 2016-10-14.13:09:00.573>
labels = ['OS-mac', '3.7']
title = 'ensurepip and pip install failures on macOS Sierra with non-system Python 2.7.x'
updated_at = <Date 2019-07-13.15:23:04.872>
user = 'https://bugs.python.org/MarcCuller'

bugs.python.org fields:

activity = <Date 2019-07-13.15:23:04.872>
actor = 'ned.deily'
assignee = 'ned.deily'
closed = False
closed_date = None
closer = None
components = ['macOS']
creation = <Date 2016-10-14.13:09:00.573>
creator = 'Marc.Culler'
dependencies = []
files = ['45090']
hgrepos = []
issue_num = 28440
keywords = ['patch']
message_count = 8.0
messages = ['278649', '278657', '279779', '282272', '282275', '311261', '347833', '347840']
nosy_count = 5.0
nosy_names = ['ronaldoussoren', 'benjamin.peterson', 'ned.deily', 'python-dev', 'Marc.Culler']
pr_nums = ['5445']
priority = None
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue28440'
versions = ['Python 2.7', 'Python 3.6', 'Python 3.7']