function to get stderr in other variable as stdout and also possible to print the output in real-time

get_all_outputs.py

def subprocess_get_all_outputs(cmd, shell=True, print_stdout=True, print_stderr=True):
    """
    behaves like a subprocess.check_output() where you can get print output 
    of stdout and stderr and both also in variables
    """
    import subprocess
    out = b''
    err = b''
    p = subprocess.Popen(cmd, shell=shell, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    while True:
        stdout_line = p.stdout.readline()
        out += stdout_line
        stderr_line = p.stderr.readline()
        err += stderr_line
        if stdout_line and print_stdout:
            print(stderr_line.decode('utf8').strip())
        if stderr_line and print_stderr:
            print(stderr_line.decode('utf8').strip())
        if stdout_line == b'' and stderr_line == b'' and p.poll() is not None:
            break
    rc = p.poll()
    return rc, out, err