Merge pull request #6 from force-h2020/six-compatibility

Six compatibility

force_bdss/data_sources/base_data_source.py

 import abc
+import six
 
 
-class BaseDataSource(metaclass=abc.ABCMeta):
+class BaseDataSource(six.with_metaclass(abc.ABCMeta)):
     def __init__(self, bundle, application, model):
         self.bundle = bundle
         self.application = application

force_bdss/mco/base_multi_criteria_optimizer.py

 import abc
+import six
 
 
-class BaseMultiCriteriaOptimizer(metaclass=abc.ABCMeta):
+class BaseMultiCriteriaOptimizer(six.with_metaclass(abc.ABCMeta)):
     def __init__(self, bundle, application, model):
         self.bundle = bundle
         self.application = application

requirements/requirements.txt

 envisage==4.6.0
 click==6.7
+six==1.10.0
+stevedore==1.24.0

setup.py

@@ -20,6 +20,7 @@ setup(
     install_requires=[
         "envisage >= 4.6.0",
         "click >= 6.7",
-        "stevedore >= 1.24.0"
+        "stevedore >= 1.24.0",
+        "six >= 1.10.0"
     ]
 )