msgpack и нестандартные типы

@ConConovaloff is already working on this.

Since Jan 30, 2015.

Если мы пакуем в msgpack не стандартный класс, то получаем ошибку.
Когда это происходит в ответе от msgpack сервера, то вызов повисает

Надо на выходе из Action рекурсивно проверять возвращаемый тип, и если он не входит в белый список, то выбрасывать исключение

https://github.com/msgpack-rpc/msgpack-rpc-python/blob/8cb1eebb65024294b2558dac1a0bb36652926a04/msgpackrpc/server.py

```
class AsyncResult:
def set_result(self, value, error=None):
if self._responder is not None:
self._responder.set_result(value, error) <----
else:
self._result = [value, error]
```

Воспроизведение ошибки:

```
Python 2.7.8 (default, Oct 30 2014, 17:51:12)
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>
>>> import msgpack
>>> packer = msgpack.Packer(default=lambda x: x.to_msgpack())
>>> packer.pack( {'some': 'wow'} )
'\x81\xa4some\xa3wow'
>>>
>>> packer.pack( 3 )
'\x03'
>>>
>>> from decimal import *
>>>
>>> Decimal(1)
Decimal('1')
>>> e = Decimal(1)
>>> packer.pack( e )
Traceback (most recent call last):
File "", line 1, in
File "msgpack/_packer.pyx", line 223, in msgpack._packer.Packer.pack (msgpack/_packer.cpp:223)
File "msgpack/_packer.pyx", line 225, in msgpack._packer.Packer.pack (msgpack/_packer.cpp:225)
File "msgpack/_packer.pyx", line 216, in msgpack._packer.Packer._pack (msgpack/_packer.cpp:216)
File "", line 1, in
AttributeError: 'Decimal' object has no attribute 'to_msgpack'
>>>
>>> type(e)

>>> type(3)

>>>

>>> con = MySQLdb.connect(...)
>>> curs = con.cursor(MySQLdb.cursors.DictCursor)
>>> curs.execute('SELECT 0.01 AS test')
1L
>>> result = curs.fetchall()
>>> type(result[0]['test'])

```

Трасировка

```

Traceback (most recent call last):
File "/opt/python/pythons/Python-2.7.8/lib/python2.7/threading.py", line 810, in __bootstrap_inner
self.run()

File "/opt/python/pythons/Python-2.7.8/lib/python2.7/site-packages/beget_msgpack/controller.py", line 62, in run
self._result.set_result(self._response.dump()) <---

File "/opt/python/pythons/Python-2.7.8/lib/python2.7/site-packages/msgpackrpc/server.py", line 67, in set_result
self._responder.set_result(value, error)

File "/opt/python/pythons/Python-2.7.8/lib/python2.7/site-packages/msgpackrpc/server.py", line 89, in set_result
self._sendable.send_message([message.RESPONSE, self._msgid, error, value])

File "/opt/python/pythons/Python-2.7.8/lib/python2.7/site-packages/msgpackrpc/transport/tcp.py", line 19, in send_message
self._stream.write(self._packer.pack(message), callback=callback)

File "msgpack/_packer.pyx", line 223, in msgpack._packer.Packer.pack (msgpack/_packer.cpp:223)
File "msgpack/_packer.pyx", line 225, in msgpack._packer.Packer.pack (msgpack/_packer.cpp:225)
File "msgpack/_packer.pyx", line 213, in msgpack._packer.Packer._pack (msgpack/_packer.cpp:213)
File "msgpack/_packer.pyx", line 184, in msgpack._packer.Packer._pack (msgpack/_packer.cpp:184)
File "msgpack/_packer.pyx", line 184, in msgpack._packer.Packer._pack (msgpack/_packer.cpp:184)
File "msgpack/_packer.pyx", line 213, in msgpack._packer.Packer._pack (msgpack/_packer.cpp:213)
File "msgpack/_packer.pyx", line 184, in msgpack._packer.Packer._pack (msgpack/_packer.cpp:184)
File "msgpack/_packer.pyx", line 216, in msgpack._packer.Packer._pack (msgpack/_packer.cpp:216)

File "/opt/python/pythons/Python-2.7.8/lib/python2.7/site-packages/msgpackrpc/transport/tcp.py", line 12, in
self._packer = msgpack.Packer(encoding=encodings[0], default=lambda x: x.to_msgpack())

AttributeError: 'Decimal' object has no attribute 'to_msgpack'
```