code: def system_call(cmd, **kwargs):
      
      proc = Popen(cmd,
                   universal_newlines=True,
                   shell=True,
                   stdout=PIPE,
                   stderr=PIPE)
      # communicate pulls all stdout/stderr from the PIPEs to
      # avoid blocking -- don't remove this line!
      stdout, stderr = proc.communicate()
      return_value = proc.returncode
  
      if return_value != 0:
          raise ValueError("Failed to execute: %s\nstdout: %s\nstderr: %s" %
                           (cmd, stdout, stderr))
  
      return stdout, stderr, return_value
docs: Call cmd and return (stdout, stderr, return_value).
  
      Parameters
      ----------
      cmd: str
          Can be either a string containing the command to be run, or a sequence
          of strings that are the tokens of the command.
      kwargs : dict, optional
          Ignored. Available so that this function is compatible with
          _redis_wrap.
  
      Notes
      -----
      This function is ported from QIIME (http://www.qiime.org), previously
      named qiime_system_call. QIIME is a GPL project, but we obtained permission
      from the authors of this function to port it to pyqi (and keep it under
      pyqi's BSD license).