Do not allow manual installation of the lab extension

We no longer ship the Jupyterlab code together with the python module, as it gets directly - and automatically - installed in the final destination.

sparkmonitor/__init__.py

@@ -5,9 +5,6 @@
 from __future__ import absolute_import
 from __future__ import unicode_literals
 
-import json
-from pathlib import Path
-
 from ._version import __version__ 
 
 def _jupyter_nbextension_paths():
@@ -19,15 +16,4 @@ def _jupyter_nbextension_paths():
         # directory in the `nbextension/` namespace
         dest='sparkmonitor',
         # _also_ in the `nbextension/` namespace
-        require='sparkmonitor/extension')]
-
-HERE = Path(__file__).parent.resolve()
-
-with (HERE / "labextension" / "package.json").open() as fid:
-    data = json.load(fid)
-
-def _jupyter_labextension_paths():
-    return [{
-        "src": "labextension",
-        "dest": data["name"]
-    }]
+        require='sparkmonitor/extension')]