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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def bulk_build(jail, pkg_file, keep=False):
    '''
    Run bulk build on poudriere server.

    Return number of pkg builds, failures, and errors, on error dump to CLI

    CLI Example:

    .. code-block:: bash

        salt -N buildbox_group poudriere.bulk_build 90amd64 /root/pkg_list

    '''
    # make sure `pkg file` and jail is on file system
    if not os.path.isfile(pkg_file):
        return 'Could not find file {0} on filesystem'.format(pkg_file)
    if not is_jail(jail):
        return 'Could not find jail {0}'.format(jail)

    # Generate command
    if keep:
        cmd = 'poudriere bulk -k -f {0} -j {1}'.format(pkg_file, jail)
    else:
        cmd = 'poudriere bulk -f {0} -j {1}'.format(pkg_file, jail)

    # Bulk build this can take some time, depending on pkg_file ... hours
    res = __salt__['cmd.run'](cmd)
    lines = res.splitlines()
    for line in lines:
        if "packages built" in line:
            return line
    return ('There may have been an issue building packages dumping output: '
            '{0}').format(res)