improve error handling around obtaining the user's Group ID

[theckman]

During why_run mode, the user has not been created yet. As such, calls to Etc.getpwnam() result in an ArgumentError being thrown.

Add a user_gid method that either returns the gid or nil, and use it where the gid is required.

[CpuID]

I wonder if taking into account the converged_by logic in http://dougireton.com/blog/2013/01/07/creating-an-lwrp-part-2/ is relevant here...?

Also, getting the below when running a converge with this:

           NoMethodError
           -------------
           undefined method `user_gid' for Chef::Resource::Directory

           Cookbook Trace:
       ---------------
           /tmp/kitchen/cache/cookbooks/user/providers/account.rb:142:in `block in home_dir_resource'
       /tmp/kitchen/cache/cookbooks/user/providers/account.rb:139:in `home_dir_resource'
       /tmp/kitchen/cache/cookbooks/user/providers/account.rb:41:in `block in class_from_file'

Chef 12.2.1

[CpuID]

I have a fix for the above error, will PR it to @theckman to merge together :)

[CpuID]

Fix for Chef 12.x / Ruby 2.x for this PR in theckman#1, so it can be merged together with this PR

[ranjib]

chef provides some built-in classes to deal with such scenarios, im thinking whether to convert the provider to leverage them. aka, define_resource_requirements
API: https://github.com/chef/chef/blob/master/lib/chef/provider.rb#L90
Usage: https://github.com/chef/chef/blob/master/lib/chef/provider/git.rb#L42

[ranjib]

also, cant we just use new_resource.username as the value of group attribute, instead of computing the gid?

[nkadel-skyhook]

Spell 'exist' correctly.