check if already bytes before encoding attempt

Author: simongarisch

pandas_datareader/compat/__init__.py

@@ -51,6 +51,8 @@ def get_filepath_or_buffer(filepath_or_buffer, encoding=None, compression=None):
 
 
 def str_to_bytes(s, encoding=None):
+    if isinstance(s, bytes):
+        return s
     return s.encode(encoding or "ascii")