glance-replicator: enable logging exceptions into log file

bug 1213779

Currently, glance-replicator provides option to enable logging
information into a specified file. But exceptions are not logged
into the log file when they are thrown.

Reproduce steps:

When setting a wrong source or target address, exceptions would be
thrown, but not logged into log file.

Change-Id: Ic2c59e04aa6099f3ede0c6b8579c31a3dfff895c

glance/cmd/replicator.py

@@ -714,6 +714,12 @@ def lookup_command(parser, command_name):
     return command
 
 
+def logging_excepthook(type, value, tb):
+    extra = {}
+    extra['exc_info'] = (type, value, tb)
+    logging.critical(str(value), **extra)
+
+
 def main():
     usage = """
 %%prog <command> [options] [args]
@@ -771,6 +777,8 @@ def main():
     else:
         handler = logging.StreamHandler(sys.stdout)
 
+    sys.excepthook = logging_excepthook
+
     if options.token:
         options.slavetoken = options.token
         options.mastertoken = options.token