Exception when block nesting is incorrect

[jokjr]

Trigger in https://github.com/tykling/ansible-roles , thanks to @tykling for the trigger.

(The problem is that we encounter endif twice and close two scopes, one of them begin the for scope. When we then try to pop the endfor scope, we get this exception.

In this case Dansabel should add an annotation and either stop parsing or try to guess what the user meant and continue.

EDIT: It looks like we should also check that what we pop is actually endfor :-)

[jokjr]

Now it looks like this :-)