use hapic reset context function

tracim/tests/__init__.py

 from tracim.fixtures import FixturesLoader
 from tracim.fixtures.users_and_groups import Base as BaseFixture
 from tracim.config import CFG
+from tracim.extensions import hapic
 from tracim import main
 from webtest import TestApp
 
             'preview_cache_dir': '/tmp/test/preview_cache',
 
         }
-        from tracim.extensions import hapic
-        hapic._context = None
+        hapic.reset_context()
         app = main({}, **settings)
         self.init_database(settings)
         self.testapp = TestApp(app)