please help me learn python exceptions

fre/pp/install.py

@@ -30,7 +30,7 @@ def _install_subtool(experiment, platform, target):
         else:
             print(f"ERROR: Workflow '{install_dir}' already installed, and the definition has changed!")
             print(f"ERROR: Please manually remove or archive your workflow run directory '{install_dir}' and then run again")
-            raise Exception
+            exit(1)
     else:
         print(f"NOTE: About to install workflow into ~/cylc-run/{name}")
         cmd = f"cylc install --no-run-name {name}"