Support for "is not" in tests

[sersorrel]

Jinja2 supports using is not for tests, like so:

{% if 4 is not divisibleby(2) %}
everything is broken
{% endif %}

It would be awesome if Tera could support the same! if not 4 is divisibleby(2) just doesn't look as nice :)

[Keats]

is not does look better but with this change if not 4 is not divisibleby(2) would also be valid and that does look ugly :/

[Keats]

I'm still not sure about that, leaving it open to collect some feedback.

[jcgruenhage]

is not does look better but with this change if not 4 is not divisibleby(2) would also be valid and that does look ugly :/

Sure, it gives people more options to make ugly expressions, but it also gives them options to avoid them, so I'd say this would be a change for the better.