[IMP] server: intercept SIGXCPU and shutdown gracefully

When the runbot spawns an Odoo instance, a CPU TIME limit is set.
When this limit is reached, the kernel kills the Odoo instance and no
message appears in the logs leaving the dev in a deep smoke cloud.

With this commit, the signal sent by the kernel when the soft
limit is reached (SIGXCPU), is intercepeted and Odoo shutdown gracefully with a
nice message for the dev.

odoo/service/server.py

@@ -207,6 +207,9 @@ class ThreadedServer(CommonServer):
                 os._exit(0)
             # interrupt run() to start shutdown
             raise KeyboardInterrupt()
+        elif sig == signal.SIGXCPU:
+            sys.stderr.write("CPU time limit exceeded! Shutting down immediately\n")
+            os._exit(0)
         elif sig == signal.SIGHUP:
             # restart on kill -HUP
             odoo.phoenix = True
@@ -266,6 +269,7 @@ class ThreadedServer(CommonServer):
             signal.signal(signal.SIGTERM, self.signal_handler)
             signal.signal(signal.SIGCHLD, self.signal_handler)
             signal.signal(signal.SIGHUP, self.signal_handler)
+            signal.signal(signal.SIGXCPU, self.signal_handler)
             signal.signal(signal.SIGQUIT, dumpstacks)
             signal.signal(signal.SIGUSR1, log_ormcache_stats)
         elif os.name == 'nt':
@@ -373,7 +377,7 @@ class GeventServer(CommonServer):
             signal.signal(signal.SIGQUIT, dumpstacks)
             signal.signal(signal.SIGUSR1, log_ormcache_stats)
             gevent.spawn(self.watchdog)
-        
+
         self.httpd = WSGIServer((self.interface, self.port), self.app)
         _logger.info('Evented Service (longpolling) running on %s:%s', self.interface, self.port)
         try: