Issue when complex objects are passed as argument

[jpmercier]

In the Python version, when called using complex Python object with __str__ method the rpc fails as the object converted to its string representation.

The fix is relatively simple:

1. Modify the FunctionCall object:
   1.1. Change the __init__ function
   1.2. Created a function call call that first get the function attrbute name of the object and then pass the args and kwargs

class FunctionCall(dict):
    """Encapsulates a function call as a Python dictionary."""

    @staticmethod
    def from_dict(dictionary):
        """Return a new FunctionCall from a Python dictionary."""
        name = dictionary.get('name')
        args = dictionary.get('args')
        kwargs = dictionary.get('kwargs')
        return FunctionCall(name, args, kwargs)

    def __init__(self, name, args=None, kwargs=None):
        """Create a new FunctionCall from a method name, an optional argument tuple, and an optional keyword argument
        dictionary."""
        self['name'] = name
        if not args:
            self['args'] = []
        else:
            self['args'] = args
        if not kwargs:
            self['kwargs'] = [{}]
        else:
            self['kwargs'] = kwargs

    def call(self, local_object):
        func = getattr(local_object, self['name'])
        return func(*self['args'], **self['kwargs'])

    def as_python_code(self):
        """Return a string representation of this object that can be evaled to execute the function call."""
        argstring = '' if 'args' not in self else \
                ','.join(str(arg) for arg in self['args'])
        kwargstring = '' if 'kwargs' not in self else \
                ','.join('%s=%s' % (key,val) for (key,val) in list(self['kwargs'].items()))
        if len(argstring) == 0:
            params = kwargstring
        elif len(kwargstring) == 0:
            params = argstring
        else:
            params = ','.join([argstring,kwargstring])
        return '%s(%s)' % (self['name'], params)

2. The Server class also needs to be modified to replace the exec statement with function_call.call(self.local_object)

class Server(object):
    """Executes function calls received from a Redis queue."""

    def __init__(self, redis_server, message_queue, local_object):
        self.redis_server = redis_server
        self.message_queue = message_queue
        self.local_object = local_object
 
    def run(self):
        # Flush the message queue.
        self.redis_server.delete(self.message_queue)
        while True:
            message_queue, message = self.redis_server.blpop(self.message_queue)
            message_queue = message_queue.decode()
            assert message_queue == self.message_queue
            logging.debug('RPC Request: %s' % message)
            transport, rpc_request = decode_message(message)
            response_queue = rpc_request['response_queue']
            function_call = FunctionCall.from_dict(rpc_request['function_call'])
            self.value = function_call.call(self.local_object)
            rpc_response = dict(return_value=self.value)
            message = transport.dumps(rpc_response)
            logging.debug('RPC Response: %s' % message)
            self.redis_server.rpush(response_queue, message)