Fix URL, fix function call

src/chatdbg/chatdbg_utils.py

@@ -83,16 +83,10 @@ def explain(source_code: str, traceback: str, exception: str, really_run=True) -
         text = completion.choices[0].message.content
         input_tokens = completion.usage.prompt_tokens
         output_tokens = completion.usage.completion_tokens
-        context_window = (
-            "8K" if model == "gpt-4" else "4K"
-        )  # FIXME: true as of Oct 3, 2023
-        cost = llm_utils.calculate_cost(
-            input_tokens, output_tokens, model, context_window
-        )
+        cost = llm_utils.calculate_cost(input_tokens, output_tokens, model)
         text += f"\n(Total cost: approximately ${cost:.2f} USD.)"
         print(llm_utils.word_wrap_except_code_blocks(text))
     except openai.error.AuthenticationError:
-        print(
-            "You need a valid OpenAI key to use ChatDBG. You can get a key here: https://openai.com/api/"
-        )
+        print("You need a valid OpenAI key to use ChatDBG.")
+        print("You can get a key here: https://platform.openai.com/api-keys")
         print("Set the environment variable OPENAI_API_KEY to your key value.")