Check that user is root only if installation is required

[faucct]

As bolt only collects custom facts in apply_prep task, which first makes sure that the agent is installed, failing fast makes it impossible to gather custom facts when running as non-root even if the agent is already installed.

[faucct]

I have checked CONTRIBUTING.md and still don't understand what needs to be fixed for CI to pass. Should my commit message have a second line?

[faucct]

I have changed the commit message to make the CI pass.
CONTRIBUTING.md could have some explanations for commit tags: I haven't found any tag that suits me and just took (maint) from recent commits without understanding what it means. Does it mean maintainer or maintenance?

[puppetcla]

Waiting for CLA signature by @faucct

@faucct - We require a Contributor License Agreement (CLA) for people who contribute to Puppet, but we have an easy click-through license with instructions, which is available at https://cla.puppet.com/

Note: if your contribution is trivial and you think it may be exempt from the CLA, please post a short reply to this comment with details. http://docs.puppet.com/community/trivial_patch_exemption.html

[puppetcla]

CLA signed by all contributors.

[donoghuc]

This looks good to me. I would defer to @puppetlabs/bolt team for final say.

[lucywyman]

lucy ~/githubs/bolt (master) $ be bolt task run puppet_agent::install -t localhost
Started on localhost...
Finished on localhost:
  10:01:01 -0700 INFO: Version parameter not defined and agent detected. Nothing to do.
Successful on 1 target: localhost
Ran on 1 target in 0.08 sec
lucy ~/githubs/bolt (master) $ vi Puppetfile ^C
lucy ~/githubs/bolt (master) $ git checkout -- Puppetfile
lucy ~/githubs/bolt (master) $ bolt puppetfile install
Successfully synced modules from /home/lucy/githubs/bolt/Puppetfile to /home/lucy/githubs/bolt/modules
lucy ~/githubs/bolt (master) $ be bolt task run puppet_agent::install -t localhost
Started on localhost...
Failed on localhost:
  The task failed with exit code 1
  puppet_agent::install task must be run as root
Failed on 1 target: localhost
Ran on 1 target in 0.07 sec

WFM