Add nested client creation method

Create nested client method

Author: SamRemis

s3transfer/crt.py

@@ -46,6 +46,7 @@
 from s3transfer.utils import (
     CallArgs,
     OSUtils,
+    create_nested_client,
     get_callbacks,
     is_s3express_bucket,
 )
@@ -481,7 +482,7 @@ def __init__(self, session, client_kwargs=None):
         if client_kwargs is None:
             client_kwargs = {}
         self._resolve_client_config(session, client_kwargs)
-        self._client = session.create_client(**client_kwargs)
+        self._client = create_nested_client(session, **client_kwargs)
         self._client.meta.events.register(
             'request-created.s3.*', self._capture_http_request
         )

s3transfer/processpool.py

@@ -214,6 +214,7 @@
     OSUtils,
     calculate_num_parts,
     calculate_range_parameter,
+    create_nested_client,
 )
 
 logger = logging.getLogger(__name__)
@@ -577,9 +578,8 @@ def __init__(self, client_kwargs=None):
 
     def create_client(self):
         """Create a botocore S3 client"""
-        return botocore.session.Session().create_client(
-            's3', **self._client_kwargs
-        )
+        session = botocore.session.Session()
+        return create_nested_client(session, 's3', **self._client_kwargs)
 
 
 class TransferMonitor:

s3transfer/utils.py

@@ -831,3 +831,18 @@ def set_default_checksum_algorithm(extra_args):
     if any(checksum in extra_args for checksum in FULL_OBJECT_CHECKSUM_ARGS):
         return
     extra_args.setdefault("ChecksumAlgorithm", DEFAULT_CHECKSUM_ALGORITHM)
+
+
+# NOTE: The following interfaces are considered private and are subject
+# to abrupt breaking changes. Please do not use them directly.
+
+try:
+    from botocore.utils import create_nested_client as create_client
+except ImportError:
+
+    def create_client(session, *args, **kwargs):
+        return session.create_client(*args, **kwargs)
+
+
+def create_nested_client(session, service_name, **kwargs):
+    return create_client(session, service_name, **kwargs)