minor fix for stablility

autogen/agentchat/conversable_agent.py

@@ -606,6 +606,8 @@ def generate_code_execution_reply(
     ):
         """Generate a reply using code execution."""
         code_execution_config = config if config is not None else self._code_execution_config
+        exitcode = None
+        exitcode2str = None
         if code_execution_config is False:
             return False, None
         if messages is None:

autogen/code_utils.py

@@ -31,7 +31,14 @@ def infer_lang(code):
     """
     if code.startswith("python ") or code.startswith("pip") or code.startswith("python3 "):
         return "sh"
-    return "python"
+
+     # check if code is a valid python code
+    try:
+        compile(code, "test", "exec")
+        return "python"
+    except SyntaxError:
+        # not a valid python code
+        return UNKNOWN
 
 
 def extract_code(
@@ -252,7 +259,7 @@ def execute_code(
     file_dir = os.path.dirname(filepath)
     os.makedirs(file_dir, exist_ok=True)
     if code is not None:
-        with open(filepath, "w") as fout:
+        with open(filepath, "w", encoding='utf-8') as fout:
             fout.write(code)
     # check if already running in a docker container
     in_docker_container = os.path.exists("/.dockerenv")