Check if an argument is given

If NOTEBOOK_PASSWORD env var is not set
this script would fail.

I also changed to use notebook.auth as is
the one in Jupyter docs for hashing passwords.

This fix #138.

run_notebook.sh

@@ -1 +1 @@
-jupyter notebook --port=8888 --no-browser --allow-root --ip=0.0.0.0 --NotebookApp.token="" --NotebookApp.password="$(python set_password.py $NOTEBOOK_PASSWORD)"
+jupyter notebook --port=8888 --no-browser --allow-root --ip=0.0.0.0 --NotebookApp.token="" --NotebookApp.password="$(./set_password.py $NOTEBOOK_PASSWORD)"

set_password.py

@@ -1,4 +1,19 @@
+#!/usr/bin/env python3
+
 import sys
-from IPython.lib import passwd
-password = passwd(sys.argv[1])
-print(password)
+
+from notebook.auth import passwd
+
+
+def run():
+    password = sys.argv[1:].pop()
+
+    if not password:
+        print('Error: Missing or empty password.', file=sys.stderr)
+    else:
+        encoded = passwd(password)
+        print(encoded)
+
+
+if __name__ == '__main__':
+    run()