freeglut (foo): failed to open display 'localhost:12.0'

[Deerzh]

my environment is a Linux server machine, which os is ubuntu18.04,
when I run this command: python -m apps.train_color --dataroot Traindata --num_sample_inout 0 --num_sample_color 5000 --sigma 0.1 --random_flip --random_scale --random_trans
an error occurred, like this:
ValueError: Sample larger than population or is negative

Can you help me solve this problem?