control: add "please install helm"

Author: mplsgrant

src/warnet/control.py

@@ -339,6 +339,10 @@ def filter(path):
     except subprocess.CalledProcessError as e:
         print(f"Failed to deploy scenario commander: {scenario_name}")
         print(f"Error: {e.stderr}")
+    except FileNotFoundError as e:
+        click.secho(e)
+        click.secho("Please install Helm.", fg="red")
+        sys.exit(1)
 
     # upload scenario files and network data to the init container
     wait_for_init(name, namespace=namespace)