fix: set mock credentials for emulator boto client (#8482)

Author: bchampp

samcli/lib/clients/lambda_client.py

@@ -53,11 +53,15 @@ def create(cls, host: str = "localhost", port: int = 5000, region: str = "us-wes
             # Create a fresh botocore session
             session = botocore.session.Session()
 
-            # Create the boto3 client with custom service model using the fresh session
+            # Create the boto3 client using the fresh session
             client = session.create_client(
                 "lambda",
                 endpoint_url=endpoint_url,
                 region_name=region,
+                # the emulator doesnt access any AWS resources,
+                # but we need _some_ credentials to create a boto client
+                aws_access_key_id="foo",
+                aws_secret_access_key="bar",
             )
 
             return cls(client)

tests/unit/lib/clients/test_lambda_client.py

@@ -44,7 +44,11 @@ def test_create_default_parameters(self, mock_session_class):
         self.assertEqual(client.client, mock_client)
         mock_session_class.assert_called_once()
         mock_session.create_client.assert_called_once_with(
-            "lambda", endpoint_url="http://localhost:5000", region_name="us-west-2"
+            "lambda",
+            endpoint_url="http://localhost:5000",
+            region_name="us-west-2",
+            aws_access_key_id="foo",
+            aws_secret_access_key="bar",
         )
 
     @patch("samcli.lib.clients.lambda_client.botocore.session.Session")
@@ -69,6 +73,8 @@ def test_create_custom_parameters(self, mock_session_class):
             "lambda",
             endpoint_url=f"http://{custom_host}:{custom_port}",
             region_name=custom_region,
+            aws_access_key_id="foo",
+            aws_secret_access_key="bar",
         )
 
     @patch("samcli.lib.clients.lambda_client.botocore.session.Session")