Handle systems with python3 (#362)

Fixes #317

Author: blink1073

jupyterlab_server/process_app.py

@@ -20,7 +20,7 @@ def get_command(self):
         """Get the command and kwargs to run with `Process`.
         This is intended to be overridden.
         """
-        return ["python", "--version"], {}
+        return [sys.executable, "--version"], {}
 
     def initialize_settings(self):
         """Start the application."""

tests/test_process.py

@@ -9,7 +9,7 @@
 
 
 def test_which():
-    assert which("python")
+    assert which("jupyter")
 
 
 async def test_process():