Create file-check functionality into utility file

There are the similar issues as PR inspec#2302. Almost resources return false
positives when a file does not exist or is not read.

Signed-off-by: ERAMOTO Masaya <[email protected]>

lib/utils/file_reader.rb

@@ -0,0 +1,25 @@
+# encoding: utf-8
+# author: ERAMOTO Masaya
+
+module FileReader
+  def read_file_content(path, allow_empty = false)
+    # these are currently ResourceSkipped to maintain consistency with the resource
+    # pre-refactor (which used skip_resource). These should likely be changed to
+    # ResourceFailed during a major version bump.
+    file = inspec.file(path)
+    if !file.file?
+      raise Inspec::Exceptions::ResourceSkipped, "Can't find file: #{path}"
+    end
+
+    raw_content = file.content
+    if raw_content.nil?
+      raise Inspec::Exceptions::ResourceSkipped, "Can't read file: #{path}"
+    end
+
+    if !allow_empty && raw_content.empty?
+      raise Inspec::Exceptions::ResourceSkipped, "File is empty: #{path}"
+    end
+
+    raw_content
+  end
+end