[phase-16]improve error message

lib/glossary_macros.rb

@@ -4,15 +4,33 @@ module GlossaryMacros
 
     desc "create macro which links to glossary term by id."
     macro :termno do |obj, args|
+      begin
+        raise 'no parameters' if args.count.zero?
+        raise 'too many parameters' if args.count > 1
         term_id = args.first
         term = GlossaryTerm.find(term_id)
         link_to term.name, project_glossary_term_path(@project, term)
+      rescue => err_msg
+        raise <<-TEXT.html_safe
+Parameter error: #{err_msg}<br>
+Usage: {{termno(glossary_term_id)}}
+TEXT
+      end
     end
 
     desc "create macro which links to glossary term by name."
     macro :term do |obj, args|
-      term = GlossaryTerm.find_by(name: args.first)
+      begin
+        raise 'no parameters' if args.count.zero?
+        raise 'too many parameters' if args.count > 1
+        term = GlossaryTerm.find_by!(name: args.first)
         link_to term.name, project_glossary_term_path(@project, term)
+      rescue => err_msg
+        raise <<-TEXT.html_safe
+Parameter error: #{err_msg}<br>
+Usage: {{term(name)}}
+TEXT
+      end
     end
 
   end