Analyse following RPM build log snippet. Describe contents accurately, without speculation or suggestions for resolution.            
Your analysis must be as concise as possible, while keeping relevant information intact.
Snippet: 
Traceback (most recent call last):
  File "/usr/bin/copr-sources-custom", line 88, in <module>
    run_cmd(mock + ['--install'] + pkgs)
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/bin/copr-sources-custom", line 64, in run_cmd
    return subprocess.check_call(command, **kwargs)
           ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/usr/lib64/python3.13/subprocess.py", line 419, in check_call
    raise CalledProcessError(retcode, cmd)
Traceback from Python runtime, caused by `CalledProcessError` exception being raised from within as script. 