To separate the assets of dev and prod environments, I was using different "export" paths.

These paths were configurated twice : For Assetic / For framework.templating in config_prod.yml and config_dev.yml.

My config_dev.yml :

framework.templating.assets_base_urls: /source

-> All my dev assets were pointing to web/source ...

Since I did the upgrade from Sf 2.6 To 2.7 Beta1, this parameter brings this exception :

InvalidArgumentException in UrlPackage.php line 129: "/source" is not a valid URL.

Is it a BC a break or a bad configuration from me ?

May be it is linked to one of these PR :
[Asset] added the component:
#13234

Twig decoupling from Templating:
#13354