[v2] Move Content-Length validation from urllib3 to botocore

.changes/next-release/bugfix-HTTP-36336.json

@@ -0,0 +1,5 @@
+{
+  "type": "bugfix",
+  "category": "HTTP",
+  "description": "Fixes regression where ``Content-Length`` validation is moved back to ``botocore`` from ``urllib3``. This re-enables functionality that depends on ``botocore``'s validation, such as resilient streaming from S3 to ``stdout`` in the case of an ``IncompleteRead``."
+}

awscli/botocore/httpsession.py

@@ -477,6 +477,7 @@ def send(self, request):
                 preload_content=False,
                 decode_content=False,
                 chunked=self._chunked(request.headers),
+                enforce_content_length=False,
             )
 
             http_response = botocore.awsrequest.AWSResponse(

tests/unit/botocore/test_http_session.py

@@ -146,6 +146,7 @@ def assert_request_sent(
             preload_content=False,
             decode_content=False,
             chunked=chunked,
+            enforce_content_length=False,
         )
 
     def _assert_manager_call(self, manager, *assert_args, **assert_kwargs):