put virtualenv activation during build in comment. That means that for the moment the build machine must be provisionned beforehand, or ansible must be available globally
<IfModule mpm_itk_module>
StartServers <%= @startservers %>
MinSpareServers <%= @minspareservers %>
MaxSpareServers <%= @maxspareservers %>
ServerLimit <%= @serverlimit %>
MaxClients <%= @maxclients %>
MaxRequestsPerChild <%= @maxrequestsperchild %>
</IfModule>