Docker API intenal server error deploying a lab

[Enrico204]

Describe the bug
While deploying a lab with lstart an error message (coming from Docker HTTP API) shows out, and the deployment stop.

Maybe is related to the way Kathara calls Docker API, see a similar issue here: projectcalico/calico#746 (comment)

To Reproduce
Steps to reproduce the behavior:

1. Download labs from https://github.com/vitome/pnd-labs.git
2. Open lab1 -> ex3
3. kathara lstart
4. See error

Expected behavior
A successful deployment.

Screenshots
Stacktrace:

user@katha:~/pnd-labs/lab1/ex3$ kathara lstart
======================= Starting Lab ========================
Description: Two lan, both with 2 pc and one router. Then, a border gateway. The assignment is: to configure the 4 pc and the three router so that the two lans are reachable and all can reach the Internet. More info in the README file.
Version: 1.1
Author(s): Angelo Spognardi
Email: spognardi@di.uniroma1.it
Website: https://sites.google.com/di.uniroma1.it/netdef1920
=============================================================
Deploying links... |########################        | 3/4
Deploying machines...CRITICAL - 500 Server Error: Internal Server Error ("failed to create endpoint kathara_user_r1_UFai4gJZF8dHiH_A4PPZMQ on network kathara_user_internal: NetworkDriver.CreateEndpoint: EOF
")

"check" Command Output

$ kathara check
*	Current Manager is: Docker (Kathara)
*	Manager version is: 18.09.7
*	Python version is: 3.6.9 (default, Nov  7 2019, 10:44:02) - [GCC 8.3.0]
*	Kathara version is: 2.2.2
*	Trying to run `Hello World` container...
Deploying links...
Deploying machines... |################################| 1/1
*	Container run successfully.
Deleting machines... |################################| 1/1
Deleting links...

[Enrico204]

Never mind, there was some previous data in Docker left in a previous attempt. docker system prune -f cleaned everything.