diff -r 84ff860a966b -r af36f459d2f0 server/repository.py
--- a/server/repository.py	Fri Oct 18 16:04:23 2013 +0200
+++ b/server/repository.py	Fri Oct 18 16:58:48 2013 +0200
@@ -36,6 +36,7 @@
 from os.path import join
 from datetime import datetime
 from time import time, localtime, strftime
+from warnings import warn
 
 from logilab.common.decorators import cached, clear_cache
 from logilab.common.compat import any
@@ -299,6 +300,8 @@
             # initialized)
             source.init(True, sourceent)
             if not source.copy_based_source:
+                warn('[3.18] old multi-source system will go away in the next version',
+                     DeprecationWarning)
                 self.sources.append(source)
                 self.querier.set_planner()
                 if add_to_cnxsets:
@@ -1665,18 +1668,24 @@
 
     @cached
     def rel_type_sources(self, rtype):
+        warn('[3.18] old multi-source system will go away in the next version',
+             DeprecationWarning)
         return tuple([source for source in self.sources
                       if source.support_relation(rtype)
                       or rtype in source.dont_cross_relations])
 
     @cached
     def can_cross_relation(self, rtype):
+        warn('[3.18] old multi-source system will go away in the next version',
+             DeprecationWarning)
         return tuple([source for source in self.sources
                       if source.support_relation(rtype)
                       and rtype in source.cross_relations])
 
     @cached
     def is_multi_sources_relation(self, rtype):
+        warn('[3.18] old multi-source system will go away in the next version',
+             DeprecationWarning)
         return any(source for source in self.sources
                    if not source is self.system_source
                    and source.support_relation(rtype))