Retry asking for password when it doesn't match or is empty (#252)

* Retry asking for password when it doesn't match or is empty

* Limit to 3 retries and let user know of add-user command on failure

* Throw error on failure

cli/utils.py

@@ -13,13 +13,19 @@ def get_ssh_key_or_prompt(ssh_key, username, password, secrets_config):
     ssh_key = get_ssh_key.get_user_public_key(ssh_key, secrets_config)
 
     if username is not None and password is None and ssh_key is None:
-        password = getpass.getpass("Please input a password for user '{0}': ".format(username))
-        confirm_password = getpass.getpass("Please confirm your password for user '{0}': ".format(username))
-        if password != confirm_password:
-            raise error.AztkError("Password confirmation did not match, please try again.")
-        if not password:
-            raise error.AztkError(
-                "Password is empty, cannot add user to cluster. Provide a ssh public key in .aztk/secrets.yaml. Or provide an ssh-key or password with commnad line parameters (--ssh-key or --password).")
+        for i in range(3):
+            if i > 0:
+                log.error("Please try again.")
+            password = getpass.getpass("Please input a password for user '{0}': ".format(username))
+            confirm_password = getpass.getpass("Please confirm your password for user '{0}': ".format(username))
+            if password != confirm_password:
+                log.error("Password confirmation did not match.")
+            elif not password:
+                log.error("Password cannot be empty.")
+            else:
+                break
+        else:
+            raise error.AztkError("Failed to get valid password, cannot add user to cluster. It is recommended that you provide a ssh public key in .aztk/secrets.yaml. Or provide an ssh-key or password with commnad line parameters (--ssh-key or --password). You may also run the 'aztk spark cluster add-user' command to add a user to this cluster.")
     return ssh_key, password
 
 def print_cluster(client, cluster: aztk.spark.models.Cluster):