When http client parses a multipart response, it always taints the headers with defects. e.g.
Use the attached file to start a simple http server, using current python exec, with commands:
```python .\example_bug.py server```
and run client with:
```python .\example_bug.py client```
which outputs:
"""[StartBoundaryNotFoundDefect(), MultipartInvariantViolationDefect()]"""

even though the multipart response is correct.
This appears to be happening because http.client, when parsing headers of response doesn't specifies the headersonly option, which leads to email.feedparser to parse response body (but http.client only passes header lines for parsing in parse_headers method, and the request body isn't available to email.feedparser).

The issue has been mentioned at:
https://github.com/shazow/urllib3/issues/800
https://github.com/Azure/azure-storage-python/issues/167

The submitted PR partially fixes the problem:
```..\python.bat .\example_bug.py client```
which outputs
"""[MultipartInvariantViolationDefect()]"""

Looks like a duplicate of Issue 29353, which has a more complete patch proposed. However, see my comment about a problem with using heartersonly=True.

My policy-flag.v2.patch for Issue 24363 may help (the details have faded from my mind, but I suspect it will either fix the problem as-is, or could be adapted).