Start a bash shell and return a :class:`REPLWrapper` object.

def bash(command="bash"):
    """Start a bash shell and return a :class:`REPLWrapper` object."""
    bashrc = os.path.join(os.path.dirname(__file__), 'bashrc.sh')
    child = pexpect.spawn(command, ['--rcfile', bashrc], echo=False,
                          encoding='utf-8')

    # If the user runs 'env', the value of PS1 will be in the output. To avoid
    # replwrap seeing that as the next prompt, we'll embed the marker characters
    # for invisible characters in the prompt; these show up when inspecting the
    # environment variable, but not when bash displays the prompt.
    ps1 = PEXPECT_PROMPT[:5] + u'\\[\\]' + PEXPECT_PROMPT[5:]
    ps2 = PEXPECT_CONTINUATION_PROMPT[:5] + u'\\[\\]' + PEXPECT_CONTINUATION_PROMPT[5:]
    prompt_change = u"PS1='{0}' PS2='{1}' PROMPT_COMMAND=''".format(ps1, ps2)

    return REPLWrapper(child, u'\\$', prompt_change,
                       extra_init_cmd="export PAGER=cat")