clean PLC log only if there is something to clean

Otherwise exception happens in Beremiz service.

Traceback (most recent call last):
File "/home/developer/WorkData/PLC/beremiz/beremiz/connectors/PYRO/_init_.py", line 113, in catcher_func
return func(*args, **kwargs)
File "/home/developer/WorkData/PLC/beremiz/beremiz/connectors/PYRO/_init_.py", line 194, in my_local_func
return RemotePLCObjectProxy._getattr_(attrName)(*args, **kwargs)
File "/usr/lib/python2.7/dist-packages/Pyro/core.py", line 381, in _call_
return self._send(self._name, args, kwargs)
File "/usr/lib/python2.7/dist-packages/Pyro/core.py", line 456, in _invokePYRO
return self.adapter.remoteInvocation(name, Pyro.constants.RIF_VarargsAndKeywords, vargs, kargs)
File "/usr/lib/python2.7/dist-packages/Pyro/protocol.py", line 457, in remoteInvocation
return self._remoteInvocation(method, flags, *args)
File "/usr/lib/python2.7/dist-packages/Pyro/protocol.py", line 532, in _remoteInvocation
answer.raiseEx()
File "/usr/lib/python2.7/dist-packages/Pyro/errors.py", line 72, in raiseEx
raise self.excObj
AttributeError: 'PLCObject' object has no attribute '_ResetLogCount'
+--- This exception occured remotely (Pyro) - Remote traceback:
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/Pyro/protocol.py", line 719, in _handleInvocation2
res = obj.Pyro_dyncall(req[1],flags,req[3]) # (method,flags,args)
File "/usr/lib/python2.7/dist-packages/Pyro/core.py", line 108, in Pyro_dyncall
return getattr(self.delegate or self,method) (args,*keywords)
File "/home/developer/WorkData/PLC/beremiz/beremiz/runtime/PLCObject.py", line 101, in ResetLogCount
if self._ResetLogCount is not None:
AttributeError: 'PLCObject' object has no attribute '_ResetLogCount'
+--- End of remote traceback

import gluon.contrib.simplejson as simplejson
import types
import sys

class JSONRPCServiceBase:

    def __init__(self):
        self.methods={}

    def response(self, id, result):
        return simplejson.dumps({'version': '1.1', 'id':id,
                                 'result':result, 'error':None})
    def error(self, id, code, message):
        return simplejson.dumps({'id': id,
                                 'version': '1.1',
                                 'error': {'name': 'JSONRPCError',
                                           'code': code,
                                           'message': message
                                           }
                                     })

    def add_method(self, name, method):
        self.methods[name] = method

    def process(self, data):
        data = simplejson.loads(data)
        id, method, params = data["id"], data["method"], data["params"]
        if method in self.methods:
            try:
                result =self.methods[method](*params)
                return self.response(id, result)
            except BaseException:
                etype, eval, etb = sys.exc_info()
                return self.error(id, 100, '%s: %s' %(etype.__name__, eval))
            except:
                etype, eval, etb = sys.exc_info()
                return self.error(id, 100, 'Exception %s: %s' %(etype, eval))
        else:
            return self.error(id, 100, 'method "%s" does not exist' % method)

    def listmethods(self):
        return self.methods.keys()