Plugin not catching exceptions

[Sylvain Avril]

Hello,

I'm writing a plugin which make an xml-rpc call that throw an
exception if the foreign call fail (due to a bad fault-structure).
So I catch this exception in my code (I expect it to fail) :
[...]
server = XMLRPC::Client.new( host, "/xmlrpc/db", 8069)
begin
result = server.call("change_admin_password", oldPassword, newPassword)
rescue Exception => e
result = 0
end
return result
[...]

When i try to execute this on the target server, I get this error :
err: Could not retrieve catalog from remote server: Error 400 on
SERVER: wrong fault-structure: {..., line 45, in check_super\n
raise Exception('AccessDenied')\nException: AccessDenied\n"} at
/etc/puppet/modules/...

When I execute the RPC call in a standalone ruby script, it work as expected.

Is there a limitation to catching exception with plugins ?
I'm a ruby beginner, may be there's a stupid mistake.

Thanks