chore: Update ModelManager error message for one model (camel-ai#1719)

Author: Wendong-Fan

camel/agents/chat_agent.py

@@ -694,11 +694,18 @@ def _get_model_response(
                 f"index: {self.model_backend.current_model_index}",
                 exc_info=exc,
             )
-        if not response:
+            error_info = str(exc)
+
+        if not response and self.model_backend.num_models > 1:
             raise ModelProcessingError(
                 "Unable to process messages: none of the provided models "
                 "run succesfully."
             )
+        elif not response:
+            raise ModelProcessingError(
+                f"Unable to process messages: the only provided model "
+                f"did not run succesfully. Error: {error_info}"
+            )
 
         logger.info(
             f"Model {self.model_backend.model_type}, "
@@ -732,11 +739,18 @@ async def _aget_model_response(
                 f"index: {self.model_backend.current_model_index}",
                 exc_info=exc,
             )
-        if not response:
+            error_info = str(exc)
+
+        if not response and self.model_backend.num_models > 1:
             raise ModelProcessingError(
                 "Unable to process messages: none of the provided models "
                 "run succesfully."
             )
+        elif not response:
+            raise ModelProcessingError(
+                f"Unable to process messages: the only provided model "
+                f"did not run succesfully. Error: {error_info}"
+            )
 
         logger.info(
             f"Model {self.model_backend.model_type}, "

camel/models/model_manager.py

@@ -117,6 +117,15 @@ def current_model_index(self) -> int:
         """
         return self.models.index(self.current_model)
 
+    @property
+    def num_models(self) -> int:
+        r"""Return the number of models in the manager.
+
+        Returns:
+            int: The number of models available in the model manager.
+        """
+        return len(self.models)
+
     @property
     def token_limit(self):
         r"""Returns the maximum token limit for current model.