docker install

I‘m tring to install agent in a docker ,then I got the following problem .

Created symlink /etc/systemd/system/multi-user.target.wants/flexiwan-router.service → /lib/systemd/system/flexiwan-router.service.
Created symlink /etc/systemd/system/multi-user.target.wants/flexiwan-router-ui.service → /lib/systemd/system/flexiwan-router-ui.service.
 * Stopping enhanced syslogd rsyslogd
   ...done.
 * Starting enhanced syslogd rsyslogd
   ...done.
gzip: /usr/share/doc/flexiwan-router/changelog.gz: No such file or directory
Usage: /usr/share/flexiwan/agent/tools/common/post_install.py <prev_version> <new_version> <install|remove>
dpkg: error processing package flexiwan-router (--configure):
 installed flexiwan-router package post-installation script subprocess returned error exit status 1
Processing triggers for libc-bin (2.27-3ubuntu1.4) ...
Processing triggers for systemd (237-3ubuntu10.51) ...

here is my DockerFile

FROM ubuntu:18.04

RUN ln -snf /usr/share/zoneinfo/Asia/Shanghai /etc/localtime && echo 'Asia/Shanghai' > /etc/timezone

RUN apt-get update
RUN apt-get install curl -y

#fix rsyslog problem
RUN apt-get install rsyslog -y
RUN sed -i 's/$PrivDropToUser/#$PrivDropToUser/g' /etc/rsyslog.conf
RUN sed -i 's/$PrivDropToGroup/#$PrivDropToGroup/g' /etc/rsyslog.conf
RUN sed -i '/imklog/s/^/#/' /etc/rsyslog.conf

RUN apt-get install gzip -y

RUN curl -sL https://deb.flexiwan.com/setup |  bash -
RUN  apt-get install -y flexiwan-router


ENTRYPOINT ["sh"]