docstr: test for bpo-42892
code: def test_get_body_malformed(self):
      """test for bpo-42892"""
      msg = textwrap.dedent(
          """\
              Message-ID: <674392CA.4347091@email.au>
              Date: Wed, 08 Nov 2017 08:50:22 +0700
              From: Foo Bar <email@email.au>
              MIME-Version: 1.0
              To: email@email.com <email@email.com>
              Subject: Python Email
              Content-Type: multipart/mixed;
              boundary="------------879045806563892972123996"
              X-Global-filter:Messagescannedforspamandviruses:passedalltests
  
              This is a multi-part message in MIME format.
              --------------879045806563892972123996
              Content-Type: text/plain; charset=ISO-8859-1; format=flowed
              Content-Transfer-Encoding: 7bit
  
              Your message is ready to be sent with the following file or link
              attachments:
              XU89 - 08.11.2017
              """
      )
      m = self._str_msg(msg)
      # In bpo-42892, this would raise
      # AttributeError: 'str' object has no attribute 'is_attachment'
      m.get_body()
  
imports: import unittest
  import textwrap
  from email import policy, message_from_string
  from email.message import EmailMessage, MIMEPart
  from test.test_email import TestEmailBase, parameterize
label_desc: Use image node_id 16 for calling the TestEmailMessage obj's underlying member method code with example usage: obj.test_get_body_malformed() without return types