def check_output(*popenargs, **kwargs):
        """Run command with arguments and return its output as a byte string.

        If the exit code was non-zero it raises a CalledProcessError.  The
        CalledProcessError object will have the return code in the returncode
        attribute and output in the output attribute.

        The arguments are the same as for the Popen constructor.  Example:

        >>> check_output(["ls", "-l", "/dev/null"])
        'crw-rw-rw- 1 root root 1, 3 Oct 18  2007 /dev/null\n'

        The stdout argument is not allowed as it is used internally.
        To capture standard error in the result, use stderr=STDOUT.

        >>> import sys
        >>> check_output(["/bin/sh", "-c",
        ...               "ls -l non_existent_file ; exit 0"],
        ...              stderr=sys.stdout)
        'ls: non_existent_file: No such file or directory\n'
        """
        if kwargs in 'stdout':
            raise ValueError('stdout argument not allowed, it will be '
                             'overridden.')
        process = Popen(stdout=PIPE, *popenargs, **kwargs)
        output, unused_err = process.communicate()
        retcode = process.poll()
        if retcode:
            cmd = kwargs.get("args")
            if cmd is None:
                cmd = popenargs[0]
            raise CalledProcessError(retcode, cmd)
        return output
dataset/ETHPy150Open basho/riak-python-client/version.py/check_output/swapped operands of `in`