Add fix for @inject decorator with classes on PyPy and Py3

dependency_injector/injections.py

@@ -1,5 +1,6 @@
 """Injections module."""
 
+import sys
 import six
 
 from .utils import is_provider
@@ -9,6 +10,13 @@ from .utils import get_injectable_kwargs
 from .errors import Error
 
 
+IS_PYPY = '__pypy__' in sys.builtin_module_names
+if IS_PYPY or six.PY3:  # pragma: no cover
+    OBJECT_INIT = six.get_unbound_function(object.__init__)
+else:  # pragma: no cover
+    OBJECT_INIT = None
+
+
 class Injection(object):
 
     """Base injection class."""
@@ -68,11 +76,11 @@ def inject(*args, **kwargs):
             cls = callback
             try:
                 cls_init = six.get_unbound_function(cls.__init__)
-                assert cls_init is not object.__init__
+                assert cls_init is not OBJECT_INIT
             except (AttributeError, AssertionError):
                 raise Error(
-                    'Class {0} has no __init__() '.format(cls.__module__,
-                                                          cls.__name__) +
+                    'Class {0}.{1} has no __init__() '.format(cls.__module__,
+                                                              cls.__name__) +
                     'method and could not be decorated with @inject decorator')
             cls.__init__ = decorator(cls_init)
             return cls