Fix for Python 3.10 (#193)
Fix for Python 3.10 (#193)

Makes GreenWithEnvy work again.

Fixes errors like

    Traceback (most recent call last):
      File "/Users/user/projects/injector/injector_test.py", line 1398, in test_newtype_integration_works
        injector = Injector([configure])
      File "/Users/user/projects/injector/injector/__init__.py", line 904, in __init__
        self.binder.install(module)
      File "/Users/user/projects/injector/injector/__init__.py", line 573, in install
        instance(self)
      File "/Users/user/projects/injector/injector_test.py", line 1396, in configure
        binder.bind(UserID, to=123)
      File "/Users/user/projects/injector/injector/__init__.py", line 474, in bind
        self._bindings[interface] = self.create_binding(interface, to, scope)
      File "/Users/user/projects/injector/injector/__init__.py", line 578, in create_binding
        provider = self.provider_for(interface, to)
      File "/Users/user/projects/injector/injector/__init__.py", line 640, in provider_for
        raise UnknownProvider('couldn\'t determine provider for %r to %r' % (interface, to))
    injector.UnknownProvider: couldn't determine provider for injector_test.UserID to 123

Fixes GH-192

alecthomas/injector