[MERGE] Forwardport of fix from 6.1 revision 4334 that sometimes caused an import error when starting a cron

bzr revid: cbi@openerp.com-20130322143046-xcdqdm8dfxngvo4o

openerp/service/cron.py

@@ -30,6 +30,7 @@ cron jobs, for all databases of a single OpenERP server instance.
 import logging
 import threading
 import time
+from datetime import datetime
 
 import openerp
 
@@ -60,6 +61,12 @@ def start_service():
     threads it spawns are not marked daemon).
 
     """
+    
+    # Force call to strptime just before starting the cron thread
+    # to prevent time.strptime AttributeError within the thread.
+    # See: http://bugs.python.org/issue7980
+    datetime.strptime('2012-01-01', '%Y-%m-%d')
+
     for i in range(openerp.tools.config['max_cron_threads']):
         def target():
             cron_runner(i)