Error: Out of pty devices

[yaya esch]

Hello everybody !
I installed ansible tower a few days ago now and when I try to run a playbook through it I get this error:

The full traceback is:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/ansible/executor/task_executor.py", line 147, in run
    res = self._execute()
  File "/usr/lib/python2.7/site-packages/ansible/executor/task_executor.py", line 620, in _execute
    self._connection = self._get_connection(cvars, templar)
  File "/usr/lib/python2.7/site-packages/ansible/executor/task_executor.py", line 957, in _get_connection
    socket_path = start_connection(self._play_context, options, self._task._uuid)
  File "/usr/lib/python2.7/site-packages/ansible/executor/task_executor.py", line 1124, in start_connection
    master, slave = pty.openpty()
  File "/usr/lib64/python2.7/pty.py", line 29, in openpty
    master_fd, slave_name = _open_terminal()
  File "/usr/lib64/python2.7/pty.py", line 70, in _open_terminal
    raise os.error, 'out of pty devices'
OSError: out of pty devices
fatal: [SW1]: FAILED! => {
    "msg": "Unexpected failure during module execution.",
    "stdout": ""

Anyone have an idea how I could solve it?