Flush stdout and add a timestamp when printing USR1-triggered status

Prints redirected to files are heavily cached, so we need to flush the
stream if we want to be able to read the output in log files as soon as
we return from signal handler.

picomon/__main__.py

@@ -45,8 +45,10 @@ def __create_report(only_old=False):
 
 def __usr1_handler(signum, frame):
     (report, err) = __create_report()
-    print ("Signal SIGUSR1 caught, printing state of checks.")
+    print ("Signal SIGUSR1 caught, printing state of checks. (%s)" %
+           datetime.now())
     print (report)
+    sys.stdout.flush()
 
 
 def __alarm_handler(signum, frame):