--- a/cubicweb/server/serverctl.py	Mon May 30 17:41:12 2016 +0200
+++ b/cubicweb/server/serverctl.py	Thu Feb 18 17:51:12 2016 +0100
@@ -35,7 +35,7 @@
 
 from logilab.database import get_db_helper, get_connection
 
-from cubicweb import AuthenticationError, ExecutionError, ConfigurationError
+from cubicweb import AuthenticationError, ExecutionError, ConfigurationError, SourceException
 from cubicweb.toolsutils import Command, CommandHandler, underline_title
 from cubicweb.cwctl import CWCTL, check_options_consistency, ConfigureInstanceCommand
 from cubicweb.server import SOURCE_TYPES
@@ -995,18 +995,25 @@
         init_cmdline_log_threshold(config, self['loglevel'])
         repo = repoapi.get_repository(config=config)
         repo.hm.call_hooks('server_maintenance', repo=repo)
+        status = 0
         try:
             try:
                 source = repo.sources_by_uri[args[1]]
             except KeyError:
                 raise ExecutionError('no source named %r' % args[1])
             with repo.internal_cnx() as cnx:
-                stats = source.pull_data(cnx, force=True, raise_on_error=True)
+                try:
+                    stats = source.pull_data(cnx, force=True, raise_on_error=True)
+                except SourceException as exc:
+                    print("can't synchronize the source:", exc)
+                    status = 1
+                    stats = {}
         finally:
             repo.shutdown()
         for key, val in stats.items():
             if val:
                 print(key, ':', val)
+        sys.exit(status)
 
 
 def permissionshandler(relation, perms):

--- a/cubicweb/server/sources/datafeed.py	Mon May 30 17:41:12 2016 +0200
+++ b/cubicweb/server/sources/datafeed.py	Thu Feb 18 17:51:12 2016 +0100
@@ -35,7 +35,7 @@
 
 from logilab.common.deprecation import deprecated
 
-from cubicweb import RegistryNotFound, ObjectNotFound, ValidationError, UnknownEid
+from cubicweb import RegistryNotFound, ObjectNotFound, ValidationError, UnknownEid, SourceException
 from cubicweb.server.repository import preprocess_inlined_relations
 from cubicweb.server.sources import AbstractSource
 from cubicweb.appobject import AppObject
@@ -172,23 +172,18 @@
                     {'x': self.eid, 'date': self.latest_retrieval})
         cnx.commit()
 
-    def acquire_synchronization_lock(self, cnx, force=False):
+    def acquire_synchronization_lock(self, cnx):
         # XXX race condition until WHERE of SET queries is executed using
         # 'SELECT FOR UPDATE'
         now = datetime.now(tz=utc)
-        if force:
-            maxdt = now
-        else:
-            maxdt = now - self.max_lock_lifetime
+        maxdt = now - self.max_lock_lifetime
         if not cnx.execute(
                 'SET X in_synchronization %(now)s WHERE X eid %(x)s, '
                 'X in_synchronization NULL OR X in_synchronization < %(maxdt)s',
                 {'x': self.eid, 'now': now, 'maxdt': maxdt}):
-            self.error('concurrent synchronization detected, skip pull')
             cnx.commit()
-            return False
+            raise SourceException("a concurrent synchronization is already running")
         cnx.commit()
-        return True
 
     def release_synchronization_lock(self, cnx):
         cnx.execute('SET X in_synchronization NULL WHERE X eid %(x)s',
@@ -206,7 +201,12 @@
         """
         if not force and self.fresh():
             return {}
-        if not self.acquire_synchronization_lock(cnx, force):
+        try:
+            self.acquire_synchronization_lock(cnx)
+        except SourceException as exc:
+            if force:
+                raise
+            self.error(str(exc))
             return {}
         try:
             if async: