json.rb produces stacktrace when a target file is unreadable

[makotots]

Description

When ini resource tries to open an unreadable file (file mode = 000), InSpec dies with backtrace.

InSpec and Platform Version

InSpec 1.8.0, Debian 7.10

Replication Case

% ls -l /tmp/unreadable
---------- 1 makoto group1 10 Dec 28 21:43 /tmp/unreadable
% cat ../test_unreadable.rb
control test_unreadable do
  describe ini('/tmp/unreadable') do
    its('foo') { should eq 'abc'}
  end
end
% bin/inspec exec ../test_unreadable.rb
/home/makoto/inspec/lib/resources/json.rb:52:in `initialize': undefined method `empty?' for nil:NilClass (NoMethodError)
....
(complete stacktrace below)

Possible Solutions

When a given file is unreadable, Train returns file.content = nil.

Expected result is returned with a patch at #1381:

% bin/inspec exec ../test_unreadable.rb

Target:  local://

  ↺  test_unreadable: INI /tmp/unreadable
     ↺  Can't read file "/tmp/unreadable"

Profile Summary: 0 successful, 0 failures, 1 skipped
Test Summary: 0 successful, 0 failures, 1 skipped
%

Happy to add a unit test if you could guide me to the standard way to mock Train objects.

Stacktrace

% bin/inspec exec ../test_unreadable.rb
/home/makoto/inspec/lib/resources/json.rb:52:in `initialize': undefined method `empty?' for nil:NilClass (NoMethodError)
	from /home/makoto/inspec/lib/inspec/plugins/resource.rb:48:in `initialize'
	from /home/makoto/inspec/lib/inspec/resource.rb:48:in `new'
	from /home/makoto/inspec/lib/inspec/resource.rb:48:in `block (3 levels) in create_dsl'
	from ../test_unreadable.rb:2:in `block in load_with_context'
	from /home/makoto/inspec/lib/inspec/rule.rb:51:in `instance_eval'
	from /home/makoto/inspec/lib/inspec/rule.rb:51:in `initialize'
	from /home/makoto/inspec/lib/inspec/control_eval_context.rb:73:in `new'
	from /home/makoto/inspec/lib/inspec/control_eval_context.rb:73:in `block (2 levels) in create'
	from ../test_unreadable.rb:1:in `load_with_context'
	from /home/makoto/inspec/lib/inspec/profile_context.rb:146:in `instance_eval'
	from /home/makoto/inspec/lib/inspec/profile_context.rb:146:in `load_with_context'
	from /home/makoto/inspec/lib/inspec/profile_context.rb:130:in `load_control_file'
	from /home/makoto/inspec/lib/inspec/profile.rb:144:in `block in collect_tests'
	from /home/makoto/inspec/lib/inspec/profile.rb:141:in `each'
	from /home/makoto/inspec/lib/inspec/profile.rb:141:in `collect_tests'
	from /home/makoto/inspec/lib/inspec/runner.rb:90:in `block in load'
	from /home/makoto/inspec/lib/inspec/runner.rb:79:in `each'
	from /home/makoto/inspec/lib/inspec/runner.rb:79:in `load'
	from /home/makoto/inspec/lib/inspec/runner.rb:100:in `run'
	from /home/makoto/inspec/lib/inspec/base_cli.rb:82:in `run_tests'
	from /home/makoto/inspec/lib/inspec/cli.rb:157:in `exec'
	from /home/makoto/local/lib/ruby/gems/2.2.0/gems/thor-0.19.4/lib/thor/command.rb:27:in `run'
	from /home/makoto/local/lib/ruby/gems/2.2.0/gems/thor-0.19.4/lib/thor/invocation.rb:126:in `invoke_command'
	from /home/makoto/local/lib/ruby/gems/2.2.0/gems/thor-0.19.4/lib/thor.rb:369:in `dispatch'
	from /home/makoto/local/lib/ruby/gems/2.2.0/gems/thor-0.19.4/lib/thor/base.rb:444:in `start'
	from bin/inspec:12:in `<main>'
%

[chris-rock]

@makotots This is a great idea. Are you going to open a PR to fix this issue?