Review App creation fails due to embedded Jinja

[artsyjian]

While embedded Jinja can be escaped using {% raw %}, it still causes problem for Review App creation.

The problem happens in 2 steps:

• Review app setup

  artsy:hokusai-sandbox jxu$ /Users/jxu/.pyenv/versions/hokusai/bin/hokusai review_app setup foo
  Created hokusai/foo.yml
  

  In this step, Hokusai loads staging.yml spec and renders any Jinja templates in the spec. This removes the raw delimiters, so that ES resource’s embedded Jinja template is no longer escaped. The produced Review App spec foo.yml contains:

      template:
        engineVersion: v2
        templateFrom:
        - literal: '{{ range $key, $value := . }}
  
            {{$key}}: {{$value | fromJson | values | first}}
  
            {{ end }}
  
            '
          target: Data
  

• Review app create

  artsy:hokusai-sandbox jxu$ /Users/jxu/.pyenv/versions/hokusai/bin/hokusai review_app create foo
  ERROR: Rendering template raised error <class 'jinja2.exceptions.TemplateSyntaxError'> <message 'unexpected char '$' at 682'>
  

  The error occurs because Hokusai attempts to Jinja render foo.yml ES resource.