Display a warning if use_docker evlauates to True but the python dock…

…er package is not available. (microsoft#172)

Co-authored-by: Qingyun Wu <qingyun.wu@psu.edu>

autogen/code_utils.py

@@ -218,7 +218,7 @@ def execute_code(
     timeout: Optional[int] = None,
     filename: Optional[str] = None,
     work_dir: Optional[str] = None,
-    use_docker: Optional[Union[List[str], str, bool]] = docker is not None,
+    use_docker: Optional[Union[List[str], str, bool]] = True,
     lang: Optional[str] = "python",
 ) -> Tuple[int, str, str]:
     """Execute code in a docker container.
@@ -257,6 +257,15 @@ def execute_code(
         logger.error(error_msg)
         raise AssertionError(error_msg)
 
+    # Warn if docker was requested but cannot be provided. In this case
+    # the current behavior is to fall back to run natively, but this behavior
+    # is subject to change.
+    if use_docker and docker is None:
+        use_docker = False
+        logger.warning(
+            "execute_code was called with use_docker evaluating to True, but the python docker package is not available. Falling back to native code execution. Note: this fallback behavior is subject to change"
+        )
+
     timeout = timeout or DEFAULT_TIMEOUT
     original_filename = filename
     if WIN32 and lang in ["sh", "shell"] and (not use_docker):