Correctly handle TooManyBuckets error_code in default_bucket method (aws#40)

* Update session.py

Correctly handles the `TooManyBuckets` error_code when the bucket already exists.

Author: jalabort

src/sagemaker/session.py

@@ -170,6 +170,13 @@ def default_bucket(self):
             elif error_code == 'OperationAborted' and 'conflicting conditional operation' in message:
                 # If this bucket is already being concurrently created, we don't need to create it again.
                 pass
+            elif error_code == 'TooManyBuckets':
+                # Succeed if the default bucket exists
+                try:
+                    s3.meta.client.head_bucket(Bucket=default_bucket)
+                    pass
+                except ClientError:
+                    raise
             else:
                 raise