title: usage of macros in dbt_project config-version:2
body: <p>Our dbt_project.yml file, config-version: 1 has two variables across different incremental models, for which one we use a macro called <em>today()</em></p>
  <pre><code>vars:
    start_date: '{{ today(offset_days=-1) }}'
    end_date: '2999-12-31'
  </code></pre>
  <p>When testing the migration to dbt 0.17.2, config-version:2, we face the following issue</p>
  <pre><code>Running with dbt=0.17.2
  Encountered an error:
  Compilation Error
    Could not render {{ today(offset_days=-1) }}: 'today' is undefined
  </code></pre>
  <p>The macro we built it end of last year. I believe dbt changed the way macro variables are referenced, however not sure how to tackle this.</p>
  <pre><code>-- returns current hour in YYYY-MM-DD-HH format,
  -- optionally offset by N days (-N or +N) or M hours (-M or +M)
  {%- macro current_hour(offset_days=0, offset_hours=0) -%}
    {%- set now = modules.datetime.datetime.now(modules.pytz.utc) -%}
    {%- set dt = now + modules.datetime.timedelta(days=offset_days, hours=offset_hours) -%}
    {{- dt.strftime(&quot;%Y-%m-%d-%H&quot;) -}}
  {%- endmacro -%}
  
  -- returns current day in YYYY-MM-DD format,
  -- optionally offset by N days (-N or +N) or M hours (-M or +M)
  {%- macro today(offset_days=0, offset_hours=0) -%}
    {{- current_hour(offset_days, offset_hours)[0:10] -}}
  {%- endmacro -%}
  
  -- accepts a timestamp string and returns a timestamo string
  -- formatted like 'YYYY-MM-DD HH24:MI:SS.US', e.g. '2019-11-02 06:11:42.690000'
  {%- macro dt_to_utc(ts_string) -%}
    TO_CHAR({{ ts_string }}::TIMESTAMPTZ, 'YYYY-MM-DD HH24:MI:SS.US')
  {%- endmacro -%}
  </code></pre>