Ensure user site packages is on PYTHONPATH for notebook test server

notebook/tests/launchnotebook.py

@@ -73,6 +73,7 @@ class NotebookTestBase(TestCase):
         data_dir = TemporaryDirectory()
         cls.env_patch = patch.dict('os.environ', {
             'HOME': cls.home_dir.name,
+            'PYTHONPATH': os.pathsep.join(sys.path),
             'IPYTHONDIR': pjoin(cls.home_dir.name, '.ipython'),
             'JUPYTER_DATA_DIR' : data_dir.name
         })
@@ -147,4 +148,4 @@ def assert_http_error(status, msg=None):
         if msg:
             assert msg in str(e), e
     else:
-        assert False, "Expected HTTP error status"
+        assert False, "Expected HTTP error status"