need a better message when terraform.tfstate not found

[mattray]

Traceback (most recent call last):
	16: from /usr/local/bin/inspec:203:in `<main>'
	15: from /usr/local/bin/inspec:203:in `load'
	14: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/inspec-bin-4.18.82/bin/inspec:11:in `<top (required)>'
	13: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/inspec-core-4.18.82/lib/inspec/base_cli.rb:35:in `start'
	12: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/base.rb:466:in `start'
	11: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor.rb:387:in `dispatch'
	10: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
	 9: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
	 8: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor.rb:238:in `block in subcommand'
	 7: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/invocation.rb:115:in `invoke'
	 6: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor.rb:387:in `dispatch'
	 5: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/invocation.rb:126:in `invoke_command'
	 4: from /opt/inspec/embedded/lib/ruby/gems/2.6.0/gems/thor-0.20.3/lib/thor/command.rb:27:in `run'
	 3: from /Users/mattray/ws/inspec-iggy/lib/inspec-iggy/terraform/cli_command.rb:83:in `generate'
	 2: from /Users/mattray/ws/inspec-iggy/lib/inspec-iggy/terraform/generate.rb:15:in `parse_generate'
	 1: from /Users/mattray/ws/inspec-iggy/lib/inspec-iggy/file_helper.rb:12:in `parse_json'
/Users/mattray/ws/inspec-iggy/lib/inspec-iggy/file_helper.rb:31:in `fetch': private method `open' called for #<URI::Generic terraform.tfstate> (NoMethodError)