What's a good equivalent to subprocess.check_call that returns the contents of stdout?

Python 2.7+

from subprocess import check_output as qx

Python < 2.7

From subprocess.py:

import subprocess
def check_output(*popenargs, **kwargs):
    if 'stdout' in kwargs:
        raise ValueError('stdout argument not allowed, it will be overridden.')
    process = subprocess.Popen(stdout=subprocess.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 subprocess.CalledProcessError(retcode, cmd, output=output)
    return output

class CalledProcessError(Exception):
    def __init__(self, returncode, cmd, output=None):
        self.returncode = returncode
        self.cmd = cmd
        self.output = output
    def __str__(self):
        return "Command '%s' returned non-zero exit status %d" % (
            self.cmd, self.returncode)
# overwrite CalledProcessError due to `output` keyword might be not available
subprocess.CalledProcessError = CalledProcessError

See also Capturing system command output as a string for another example of possible check_output() implementation.