Fix flaky server tests.

Force stop the jupyter server when the test is done to avoid it sticking
around.

Force test_user_client to use a free port instead of a potentially in
use one.

http://b/277579939
http://b/277898785

Author: djherbis

tests/test_jupyterlab_lsp.py

@@ -2,6 +2,7 @@
 import unittest
 
 from jupyter_server.serverapp import ServerApp
+import subprocess
 
 # Adapted from:
 # https://github.com/jupyter-lsp/jupyterlab-lsp/blob/ce76fab170feea506faf9ef47e4bd6a468c24313/python_packages/jupyter_lsp/jupyter_lsp/tests/test_extension.py
@@ -30,3 +31,7 @@ def test_serverextension(self):
         self.assertTrue(found_lsp, "didn't install the /lsp/ route")
         app.stop()
 
+        strpid=subprocess.Popen("ps -ef | grep jupyter | grep 9999 | awk '{print $2}' | head -n 1", shell=True, stdout=subprocess.PIPE).stdout.read().decode("utf-8").strip()
+        if strpid != "":
+            pid=int(strpid)
+            os.kill(pid, 9)

tests/test_user_secrets.py

@@ -40,7 +40,7 @@ def do_POST(s):
 
 
 class TestUserSecrets(unittest.TestCase):
-    SERVER_ADDRESS = urlparse(os.getenv(_KAGGLE_URL_BASE_ENV_VAR_NAME, default="http://127.0.0.1:8001"))
+    SERVER_ADDRESS = urlparse(os.getenv(_KAGGLE_URL_BASE_ENV_VAR_NAME, default="http://127.0.0.1:0"))
 
     def _test_client(self, client_func, expected_path, expected_body, secret=None, success=True):
         _request = {}