Fix lint errors for promise-reject-errors

Change-Id: I7d21e3bfaa81a21e5a5fc864ca09db17dc92abd8

polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor_test.html

diff --git a/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor_test.html b/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor_test.html
index 8607948..1785d1f 100644
--- a/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor_test.html
+++ b/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor_test.html
@@ -155,7 +155,7 @@
       const newKeyString = 'not even close to valid';
 
       const addStub = sinon.stub(element.$.restAPI, 'addAccountSSHKey',
-          () => { return Promise.reject(); });
+          () => { return Promise.reject(new Error('error')); });
 
       element._newKey = newKeyString;