Properly prevent sending XML files opened in text mode

arkindex/client.py

@@ -8,7 +8,7 @@ import yaml
 from arkindex.auth import TokenSessionAuthentication
 from arkindex.pagination import ResponsePaginator
 from arkindex.encoders import XMLEncoder
-from io import FileIO
+from io import IOBase, BufferedIOBase
 from time import sleep
 from urllib.parse import urlsplit, urlunsplit
 
@@ -183,8 +183,8 @@ class ArkindexClient(apistar.Client):
         :param kwargs: Other arguments sent to :meth:`ArkindexClient.custom_request`.
         """
 
-        if isinstance(body, FileIO):
-            assert body.mode == 'rb', 'File-like objects should be opened in binary mode'
+        if isinstance(body, IOBase):
+            assert isinstance(body, BufferedIOBase), 'File-like objects should be opened in binary mode'
 
         return self.custom_request(
             operation_id,