AttributeError: 'NoneType' object has no attribute 'cvtColor'

I get the following error on running: python train.py --algo a2c --env SpaceInvadersNoFrameskip-v4

Terminal Output:

========== SpaceInvadersNoFrameskip-v4 ==========
Seed: 1398960405
Default hyperparameters for environment (ones being tuned will be overridden):
OrderedDict([('ent_coef', 0.01),
             ('env_wrapper',
              ['stable_baselines3.common.atari_wrappers.AtariWrapper']),
             ('frame_stack', 4),
             ('n_envs', 16),
             ('n_timesteps', 10000000.0),
             ('policy', 'CnnPolicy'),
             ('policy_kwargs',
              'dict(optimizer_class=RMSpropTFLike, '
              'optimizer_kwargs=dict(eps=1e-5))'),
             ('vf_coef', 0.25)])
Using 16 environments
Creating test environment
Stacking 4 frames
Wrapping into a VecTransposeImage
Stacking 4 frames
Wrapping into a VecTransposeImage
Using cuda device
Log path: logs/a2c/SpaceInvadersNoFrameskip-v4_4
Traceback (most recent call last):
  File "train.py", line 178, in <module>
    exp_manager.learn(model)
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/utils/exp_manager.py", line 189, in learn
    model.learn(self.n_timesteps, **kwargs)
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/stable_baselines3/a2c/a2c.py", line 198, in learn
    reset_num_timesteps=reset_num_timesteps,
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/stable_baselines3/common/on_policy_algorithm.py", line 227, in learn
    total_timesteps, eval_env, callback, eval_freq, n_eval_episodes, eval_log_path, reset_num_timesteps, tb_log_name
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/stable_baselines3/common/base_class.py", line 420, in _setup_learn
    self._last_obs = self.env.reset()  # pytype: disable=annotation-type-mismatch
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/stable_baselines3/common/vec_env/vec_transpose.py", line 98, in reset
    return self.transpose_observations(self.venv.reset())
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/stable_baselines3/common/vec_env/vec_frame_stack.py", line 58, in reset
    observation = self.venv.reset()  # pytype:disable=annotation-type-mismatch
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/stable_baselines3/common/vec_env/dummy_vec_env.py", line 61, in reset
    obs = self.envs[env_idx].reset()
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/gym/core.py", line 237, in reset
    return self.env.reset(**kwargs)
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/gym/core.py", line 277, in reset
    return self.env.reset(**kwargs)
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/gym/core.py", line 265, in reset
    return self.observation(observation)
  File "/home/ubuntu/src/rl-baselines3/rl-baselines3-zoo/.venv/lib/python3.7/site-packages/stable_baselines3/common/atari_wrappers.py", line 202, in observation
    frame = cv2.cvtColor(frame, cv2.COLOR_RGB2GRAY)
AttributeError: 'NoneType' object has no attribute 'cvtColor'

[fiberleif]

can you please tell me what was the issue?

“pip install opencv-python” is ok for me.

[bkpcoding]

I resolved the issue, so I had a problem with my installation. I didn’t install libx11. I came to know about the issue by running import cv2 in python interactive session on my container. I don’t know why the baselines compresses this error message 😦