Update app.py

app.py

@@ -2,6 +2,13 @@
 import tiktoken
 import openai
 from openai.error import InvalidRequestError
+import openai
+
+# some versions expose exceptions under openai.error, others at the root
+try:
+    from openai.error import InvalidRequestError
+except ImportError:
+    InvalidRequestError = openai.InvalidRequestError
 
 # Choose your model and its max context size
 MODEL_NAME    = "gpt-4-32k"