Refactoring method to leverage safe_constantize

lib/qa.rb

@@ -84,18 +84,12 @@ class DataNormalizationError < StandardError; end
   # @return [#search, #find, #fetch]
   def self.authority_for(vocab:, subauthority: nil)
     authority_constant_name = "Qa::Authorities::#{vocab.to_s.camelcase}"
-    begin
-      authority_constant = authority_constant_name.constantize
-    rescue NameError
-      raise Qa::InvalidAuthorityError, authority_constant_name
-    end
+    authority_constant = authority_constant_name.safe_constantize
+    raise Qa::InvalidAuthorityError, authority_constant_name if authority_constant.nil?
 
-    if authority_constant.is_a?(Class)
-      authority_constant.new
-    elsif subauthority.present?
-      authority_constant.subauthority_for(subauthority)
-    else
-      raise Qa::MissingSubAuthority, "No sub-authority provided"
-    end
+    return authority_constant.new if authority_constant.is_a?(Class)
+    return authority_constant.subauthority_for(subauthority) if subauthority.present?
+
+    raise Qa::MissingSubAuthority, "No sub-authority provided"
   end
 end