Dockerfile with warnings breaks verbose boatswain

[sverhoeven]

A verbose boatswain build dies when a Dockerfile generates warnings during build.

Example files:

Dockerfile file:

FROM alpine

RUN hostname && \

# make room
date

The empty line after RUN will generate warnings.

boatswain.yml file:

version: 1.0
organisation: nlesc
images:
  sometest:
    context: .

Tested with Docker v19.03.1 and boatswain 1.0.3

Use docker build works:

docker build -t nlesc/sometest .
Sending build context to Docker daemon  10.24kB
[WARNING]: Empty continuation line found in:
    RUN hostname && date
[WARNING]: Empty continuation lines will become errors in a future release.
Step 1/2 : FROM alpine
 ---> cdf98d1859c1
Step 2/2 : RUN hostname && date
 ---> Using cache
 ---> 9045f64ed928
Successfully built 9045f64ed928
Successfully tagged nlesc/sometest:latest

Use boatswain build also works:

docker rmi nlesc/sometest
boatswain build 
Welcome to Boatswain
sometest             100% (2 of 2) │██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████│ Elapsed Time: 0:00:01

Build summary
built:
    sometest
Final result was deemed a: success

But using -v or -v -v fails with:

docker rmi nlesc/sometest
boatswain build -v
Welcome to Boatswain
Now building sometest in directory . and tagging as nlesc/sometest
----------           100% (1 of 1) │██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████│ Elapsed Time: 0:00:01
Traceback (most recent call last):
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/bin/boatswain", line 10, in <module>
    sys.exit(main())
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/cli.py", line 181, in main
    result = bosun.build(dryrun=arguments.dryrun, force=arguments.force)
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/boatswain.py", line 99, in build
    return self._do_action('build', dryrun=dryrun, force=force)
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/boatswain.py", line 118, in _do_action
    return self._do_action_dict(action, self.images, **kwargs)
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/boatswain.py", line 148, in _do_action_dict
    return self.build_list(names, images, **kwargs)
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/boatswain.py", line 252, in build_list
    if self.build_one(name, definition, dryrun=dryrun, force=force):
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/boatswain.py", line 405, in build_one
    ident = self._docker_progress(name, generator)
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/boatswain.py", line 563, in _docker_progress
    self.progress_bar.update()
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/boatswain/timed_progress_bar.py", line 35, in update
    self.progress_bar.update(self.step, imagename=self.imagename)
  File "/home/verhoes/.local/share/virtualenvs/q-VtrXc7DU/lib/python3.6/site-packages/progressbar/bar.py", line 568, in update
    % (value, self.min_value, self.max_value))
ValueError: Value 2 is out of range, should be between 0 and 1

The image is build, but boatswain dies.

Also the warnings from Docker are not shown.