Fix Method to be non positional as there is a randomly happening bug that I cannot trace.

tests/test_config_method.py

@@ -15,7 +15,6 @@ class MethodBasedConfigurable(Configurable):
 
 def test_one_wrapper_only():
     with pytest.raises(ConfigurationError):
-
         class TwoMethods(Configurable):
             h1 = Method()
             h2 = Method()
@@ -28,7 +27,12 @@ def test_define_with_decorator():
     def Concrete(self, *args, **kwargs):
         calls.append((args, kwargs, ))
 
+    print('handler', Concrete.handler)
+
+    assert callable(Concrete.handler)
     t = Concrete('foo', bar='baz')
+
+    assert callable(t.handler)
     assert len(calls) == 0
     t()
     assert len(calls) == 1
@@ -41,6 +45,7 @@ def test_define_with_argument():
         calls.append((args, kwargs, ))
 
     t = MethodBasedConfigurable('foo', bar='baz', handler=concrete_handler)
+    assert callable(t.handler)
     assert len(calls) == 0
     t()
     assert len(calls) == 1
@@ -54,6 +59,7 @@ def test_define_with_inheritance():
             calls.append((args, kwargs, ))
 
     t = Inheriting('foo', bar='baz')
+    assert callable(t.handler)
     assert len(calls) == 0
     t()
     assert len(calls) == 1
@@ -69,7 +75,9 @@ def test_inheritance_then_decorate():
     def Concrete(self, *args, **kwargs):
         calls.append((args, kwargs, ))
 
+    assert callable(Concrete.handler)
     t = Concrete('foo', bar='baz')
+    assert callable(t.handler)
     assert len(calls) == 0
     t()
     assert len(calls) == 1