<div id="rep-src-iframe-container">
  <div id="email-progress-bar" class="progress"
       style="display: none; position: absolute; z-index: -1; width: 100%; text-align: center">
    <div class="progress-bar progress-bar-striped active">
      <%= t 'rep.base.loading' %>
    </div>
  </div>

  <iframe id="rep-src-iframe" srcdoc="<%= @mail_body_html.to_str %>" seamless="seamless"></iframe>
  <%= javascript_tag render(template: 'rails_email_preview/emails/email_iframe.js'),
                     **(RailsEmailPreview.rails_supports_csp_nonce? ? {nonce: true} : {}) %>
</div>

<div id="rep-src-iframe-container">
  <div id="email-progress-bar" class="progress"
       style="display: none; position: absolute; z-index: -1; width: 100%; text-align: center">
    <div class="progress-bar progress-bar-striped active">
      <%= t 'rep.base.loading' %>
    </div>
  </div>

  <iframe id="rep-src-iframe" srcdoc="<%= @mail_body_html.to_str %>" seamless="seamless"></iframe>
  <%= javascript_tag render(template: 'rails_email_preview/emails/email_iframe', formats: [:js]),
                     **(RailsEmailPreview.rails_supports_csp_nonce? ? {nonce: true} : {}) %>
</div>

Fix deprecation warning re. filename in render call
Fix deprecation warning re. filename in render call
