ServerProxy should not make requests with malformed XML

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2017-07-12.15:22:13.721>
labels = ['expert-XML', 'type-bug', '3.7']
title = 'ServerProxy should not make requests with malformed XML'
updated_at = <Date 2017-07-12.16:34:07.700>
user = 'https://bugs.python.org/AlexCorcoles'

bugs.python.org fields:

activity = <Date 2017-07-12.16:34:07.700>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['XML']
creation = <Date 2017-07-12.15:22:13.721>
creator = 'Alex Corcoles'
dependencies = []
files = []
hgrepos = []
issue_num = 30909
keywords = []
message_count = 2.0
messages = ['298226', '298233']
nosy_count = 2.0
nosy_names = ['serhiy.storchaka', 'Alex Corcoles']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = None
status = 'open'
superseder = '7727'
type = 'behavior'
url = 'https://bugs.python.org/issue30909'
versions = ['Python 2.7', 'Python 3.3', 'Python 3.4', 'Python 3.5', 'Python 3.6', 'Python 3.7']