Remove jupyterlab from the extension every time we build

setup.py

@@ -12,6 +12,7 @@ from subprocess import check_call
 import os
 import sys
 import platform
+import shutil
 
 here = os.path.dirname(os.path.abspath(__file__))
 node_root = os.path.join(here, 'jupyterlab')
@@ -102,6 +103,8 @@ class NPM(Command):
 
         if self.should_run_npm_install():
             log.info("Installing build dependencies with npm.  This may take a while...")
+            # remove just jupyterlab
+            shutil.rmtree(os.path.join(node_root, 'node_modules', 'jupyterlab'), ignore_errors=True)
             check_call(['npm', 'install'], cwd=node_root, stdout=sys.stdout, stderr=sys.stderr)
             check_call(['npm', 'run', 'build'], cwd=node_root, stdout=sys.stdout, stderr=sys.stderr)
             os.utime(self.node_modules, None)