Update request urllib3 (#464)

* requests: updated to version 2.27.1

* urllib3: updated to version 1.26.18

lib/urllib3/util/response.py

@@ -1,7 +1,9 @@
 from __future__ import absolute_import
-from ..packages.six.moves import http_client as httplib
+
+from email.errors import MultipartInvariantViolationDefect, StartBoundaryNotFoundDefect
 
 from ..exceptions import HeaderParsingError
+from ..packages.six.moves import http_client as httplib
 
 
 def is_fp_closed(obj):
@@ -42,8 +44,7 @@ def assert_header_parsing(headers):
 
     Only works on Python 3.
 
-    :param headers: Headers to verify.
-    :type headers: `httplib.HTTPMessage`.
+    :param http.client.HTTPMessage headers: Headers to verify.
 
     :raises urllib3.exceptions.HeaderParsingError:
         If parsing errors are found.
@@ -66,6 +67,25 @@ def assert_header_parsing(headers):
 
             if isinstance(payload, (bytes, str)):
                 unparsed_data = payload
+    if defects:
+        # httplib is assuming a response body is available
+        # when parsing headers even when httplib only sends
+        # header data to parse_headers() This results in
+        # defects on multipart responses in particular.
+        # See: https://github.com/urllib3/urllib3/issues/800
+
+        # So we ignore the following defects:
+        # - StartBoundaryNotFoundDefect:
+        #     The claimed start boundary was never found.
+        # - MultipartInvariantViolationDefect:
+        #     A message claimed to be a multipart but no subparts were found.
+        defects = [
+            defect
+            for defect in defects
+            if not isinstance(
+                defect, (StartBoundaryNotFoundDefect, MultipartInvariantViolationDefect)
+            )
+        ]
 
     if defects or unparsed_data:
         raise HeaderParsingError(defects=defects, unparsed_data=unparsed_data)
@@ -76,8 +96,9 @@ def is_response_to_head(response):
     Checks whether the request of a response has been a HEAD-request.
     Handles the quirks of AppEngine.
 
-    :param conn:
-    :type conn: :class:`httplib.HTTPResponse`
+    :param http.client.HTTPResponse response:
+        Response to check if the originating request
+        used 'HEAD' as a method.
     """
     # FIXME: Can we do this somehow without accessing private httplib _method?
     method = response._method