Easy to recreate:

* create a new blank .twig file somewhere with the following contents:
<tr class="{{cycle(['even', 'odd'], 4)}}"></tr>

you should see: "Unexpected token LBRACE found" in the action items window.

if you add any character before or after the double curly braces, the error goes away:
<tr class="a{{ }}"></tr>
<tr class="{{ }}b"></tr>

both the above are OK (no error), but in between the braces - and you have the error again:

shows error:
<tr class="{{a}}"></tr>

so I guess that the parser is looking for some alpha character between the class="" quotes, and not recognizing any twig functions between double braces, and throwing the LBRACE error.