Fix typo in error message (#687)

src/smolagents/agents.py

@@ -388,7 +388,7 @@ def execute_tool_call(self, tool_name: str, arguments: Union[Dict[str, str], str
             if tool_name in self.tools:
                 tool = self.tools[tool_name]
                 error_msg = (
-                    f"Error whene executing tool {tool_name} with arguments {arguments}: {type(e).__name__}: {e}\nYou should only use this tool with a correct input.\n"
+                    f"Error when executing tool {tool_name} with arguments {arguments}: {type(e).__name__}: {e}\nYou should only use this tool with a correct input.\n"
                     f"As a reminder, this tool's description is the following: '{tool.description}'.\nIt takes inputs: {tool.inputs} and returns output type {tool.output_type}"
                 )
                 raise AgentExecutionError(error_msg, self.logger)