ssh connection plugin: Report missing sudo password

If no password is provided, sudo hangs at the prompt. Identify this and
report that the password is missing as an error.

lib/ansible/runner/connection_plugins/ssh.py

@@ -155,12 +155,17 @@ class Connection(object):
             rfd, wfd, efd = select.select(rpipes, [], rpipes, 1)
 
             # fail early if the sudo/su password is wrong
-            if self.runner.sudo and sudoable and self.runner.sudo_pass:
+            if self.runner.sudo and sudoable:
+                if self.runner.sudo_pass:
                     incorrect_password = gettext.dgettext(
                         "sudo", "Sorry, try again.")
-                if stdout.endswith("%s\r\n%s" % (incorrect_password, prompt)):
+                    if stdout.endswith("%s\r\n%s" % (incorrect_password,
+                                                     prompt)):
                         raise errors.AnsibleError('Incorrect sudo password')
 
+                if stdout.endswith(prompt):
+                    raise errors.AnsibleError('Missing sudo password')
+
             if self.runner.su and su and self.runner.sudo_pass:
                 incorrect_password = gettext.dgettext(
                     "su", "Sorry")