The customJsx E2E test occasionally failed at login with the form
showing 'This field is required' on the username, because the submit
button was clicked while the form was still hydrating (it is disabled
until mounted) and the field values were reset by the re-mount. Wait
for the submit button to become enabled before filling, and assert the
username value stuck before submitting.
Thomas Camlong
926b7e2a5e