import fails when Dockerfile contains tabs instead of spaces

ISSUE TYPE

Bug Report

container.yml

there's no container.yml yet

# ansible-container --project-path target import ./old

OS / ENVIRONMENT

# ansible-container --debug version
Ansible Container, version 0.9.2
Linux, 94d26d51335e, 4.4.0-96-generic, #119-Ubuntu SMP Tue Sep 12 14:59:54 UTC 2017, x86_64
2.7.12 (default, Nov 19 2016, 06:48:10)
[GCC 5.4.0 20160609] /usr/bin/python

SUMMARY

Import fails when Dockerfile has tabs between directive and payload. As soon as the tabs are replace with spaces, it works.

STEPS TO REPRODUCE

have a dockerfile like

FROM<tab>ubuntu

in ./old run

# ansible-container --project-path target import ./old

EXPECTED RESULTS

No failures, import producing output

ACTUAL RESULTS

ERROR   Unknown exception
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/container/cli.py", line 299, in __call__
    getattr(core, u'hostcmd_{}'.format(args.subcommand))(**vars(args))
  File "/usr/local/lib/python2.7/dist-packages/container/__init__.py", line 28, in __wrapped__
    return fn(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/container/core.py", line 475, in hostcmd_import
    engine_obj.import_project(base_path, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/container/__init__.py", line 28, in __wrapped__
    return fn(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/container/docker/engine.py", line 1096, in import_project
    dfi.run()
  File "/usr/local/lib/python2.7/dist-packages/container/docker/importer.py", line 506, in run
    (list(parser), os.path.join(self.role_path, 'tasks', 'main.yml')),
  File "/usr/local/lib/python2.7/dist-packages/container/docker/importer.py", line 170, in __iter__
    for preparsed in self.preparse_iter():
  File "/usr/local/lib/python2.7/dist-packages/container/docker/importer.py", line 146, in preparse_iter
    directive, payload = line.split(u' ', 1)
ValueError: need more than 1 value to unpack

ansible / ansible-container

import fails when Dockerfile contains tabs instead of spaces #754