False positive on the use of SUDO

[ghost]

Issue details

I have a Dockerfile containing the following line:
RUN echo "jenkins ALL=(ALL) ALL" >> etc/sudoers
which to my knowledge is not running a command with sudo

if i run dockerlint Dockefile, i get the following message

WARN: sudo(8) usage found on line 35 which is discouraged

[reverbc]

Same symptom but (slightly) different approach here:
RUN yum install -y sudo

This line gets the same warning message and should also be a false positive.

[iamramin]

I've just got this false positive with the sudo package listed on a separate line like this:

RUN yum install -y \
    sudo