Add error event handler to ssh-keygen child_process

Fixes #2255

packages/node_modules/@node-red/runtime/lib/storage/localfilesystem/projects/ssh/keygen.js

@@ -51,6 +51,12 @@ function runSshKeygenCommand(args,cwd,env) {
                 resolve(stdout);
             }
         });
+        child.error('error', function(err) {
+            if (/ENOENT/.test(err.toString())) {
+                err.code = "command_not_found";
+            }
+            reject(err);
+        });
     });
 }