fixed s3 default endpoint url

harvester/source/s3.py

@@ -25,7 +25,7 @@ class S3Source(Source):
         bucket: str,
         secret_access_key: str = None,
         access_key_id: str = None,
-        endpoint_url: str = "",
+        endpoint_url: str = None,
         validate_bucket_name: bool = True,
         region_name: str = None,
         public: bool = False,
@@ -82,6 +82,7 @@ class S3Source(Source):
 
     def open(self, path: str) -> IO[AnyStr]:
         bucket, key = self.get_bucket_and_key(path)
+        logger.debug("bucket, key: %s, %s", bucket, key)
         return self.client.get_object(Bucket=bucket, Key=key)["Body"]
 
     def stat(self, path: str) -> Stat: