Add Python coverage make target(s)

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-02-16.19:45:02.130>
labels = ['type-feature', '3.7', 'build']
title = 'Add Python coverage make target(s)'
updated_at = <Date 2017-02-16.19:56:34.233>
user = 'https://github.com/zware'

bugs.python.org fields:

activity = <Date 2017-02-16.19:56:34.233>
actor = 'barry'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Build']
creation = <Date 2017-02-16.19:45:02.130>
creator = 'zach.ware'
dependencies = []
files = []
hgrepos = []
issue_num = 29582
keywords = []
message_count = 2.0
messages = ['287968', '287969']
nosy_count = 2.0
nosy_names = ['barry', 'zach.ware']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue29582'
versions = ['Python 3.7']