code_utils.py powershell command bugfix in MacOS

autogen/code_utils.py

@@ -229,21 +229,29 @@ def get_powershell_command():
                 return "pwsh"
 
         except (FileNotFoundError, NotADirectoryError):
-            if WIN32:
-                logging.warning("Neither powershell nor pwsh is installed but it is a Windows OS")
-            return None
+            if WIN32 and FileNotFoundError:
+                logging.warning("Neither powershell.exe nor pwsh.exe is present but it is a Windows OS")
+
+            elif WIN32 and NotADirectoryError:
+                logging.warning(
+                    "PowerShell is either not installed or its path is not given properly in the environment variable PATH. Please check the path and try again."
+                )
 
+            return None
 
-powershell_command = get_powershell_command()
+    except PermissionError:
+        logging.warning("The application has no permission to run powershell")
+        return None
 
 
 def _cmd(lang):
-    if lang.startswith("python") or lang in ["bash", "sh", powershell_command]:
+    if lang.startswith("python") or lang in ["bash", "sh"]:
         return lang
     if lang in ["shell"]:
         return "sh"
     if lang in ["ps1", "pwsh", "powershell"]:
-        return powershell_command
+        powershell_command = get_powershell_command()
+        return powershell_command if powershell_command is not None else "sh"
 
     raise NotImplementedError(f"{lang} not recognized in code execution")