python destination with python3, can not process msg.MSG

[mitzkia]

I got python exception when I wanted to use msg.MSG from python script with python3 interpreter

Reproduction:

• configure syslog-ng with "with-python=3" option
• create separate python script file with the following content
• sngexample.py

class DummyPythonDest(object):
    def init(self, options):
        return True

    def send(self, msg):
        print("send: %s\n" % msg.MSG)
        return True

• start syslog-ng with the given config

@version: 3.9
source s_net {tcp( ip("127.0.0.1") port(6666) );};
destination d_python {
  python(
    class("sngexample.DummyPythonDest")
  );
};
log {
  source(s_net);
  destination(d_python);
};

• send message to syslog-ng with loggen
• got following exception

[2017-03-06T15:08:32.136246] Incoming log entry; line='<38>2017-03-06T15:08:32 localhost prg00000[1234]: seq: 0000000000, thread: 0000, runid: 1488809312, stamp: 2017-03-06T15:08:32 PADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADDPADD'
[2017-03-06T15:08:32.136638] EOF occurred while reading; fd='15'
[2017-03-06T15:08:32.141016] Syslog connection closed; fd='15', client='AF_INET(127.0.0.1:52600)', local='AF_INET(127.0.0.1:6666)'
[2017-03-06T15:08:32.141118] Closing log transport fd; fd='15'
Traceback (most recent call last):
  File "/home/micek/micek_work/micek_syslog_ng_python_scripts/sngexample.py", line 8, in send
    print(msg.MSG)
SystemError: error return without exception set
[2017-03-06T15:08:32.211917] g_strlcpy: assertion 'src != NULL' failed
TypeError: expected bytes, str found
[2017-03-06T15:08:32.212136] Exception while calling a Python function; module='d_python#0', script='sngexample.DummyPythonDest', function='P\xa8\x0e\xd0r', exception='None'

[furiel]

Instead of
print("send: %s\n" % msg.MSG)
this needs to be used:
print("send: %s\n" % msg["MESSAGE"])

[lbudai]

From #1371 only msg['MSG'] form is supported.