Add python 3 support

api.py

@@ -14,10 +14,10 @@ except ImportError:
     raise Exception(message)
 
 __all__ = ['CarrierApi']
-__metaclass__ = PoolMeta
 
 
 class CarrierApi:
+    __metaclass__ = PoolMeta
     __name__ = 'carrier.api'
 
     @classmethod

manifest.py

@@ -7,10 +7,10 @@ from trytond.transaction import Transaction
 from base64 import decodestring
 
 __all__ = ['CarrierManifest']
-__metaclass__ = PoolMeta
 
 
 class CarrierManifest:
+    __metaclass__ = PoolMeta
     __name__ = 'carrier.manifest'
 
     def get_manifest_seurvalencia(self, api, from_date, to_date):

shipment.py

@@ -9,12 +9,12 @@ import logging
 import tempfile
 
 __all__ = ['ShipmentOut']
-__metaclass__ = PoolMeta
 
 logger = logging.getLogger(__name__)
 
 
 class ShipmentOut:
+    __metaclass__ = PoolMeta
     __name__ = 'stock.shipment.out'
 
     @classmethod