At http://en.m.wikipedia.beta.wmflabs.org click Create Account
enter a user name, a password, and a confirm-password that does not match the password. Click 'Sign up'
User should see an error message but does not.
Behavior is the same when entering the CAPTCHA, although that should not be necessary.
This is the failure at https://integration.wikimedia.org/ci/view/BrowserTests/view/-All/job/browsertests-MobileFrontend-en.m.wikipedia.beta.wmflabs.org-linux-chrome-sauce/436/testReport/(root)/Create%20failure%20messages/Create_account_password_mismatch_message/