app/views/admin/merchandise/variants/edit.html.erb
<%= render partial: '/admin/merchandise/sub_header'%>
<h2>Edit Variant (<%= @product.name %>)</h2>
<%= form_for @variant, url: admin_merchandise_product_variant_path(@product, @variant),
html: { class: ''} do |form| %>
<%= render partial: '/admin/merchandise/variants/form', locals: { form: form } %>
<div class=" generic_submit_button">
<%= submit_tag "Update",
class: "button",
id: "create_variant_button" %>
</div>
<% end %>