No such file or directory

[typo3ua]

I did...

Copy flexible_include.rb into /_plugins

then...

{% flexible_include '/assets/js/my.js' %}

or...

{% flexible_include 'assets/js/my.js' %}

I get error

flexible_include.rb: No such file or directory @ rb_sysopen - /assets/js/my.js
  Liquid Exception: flexible_include.rb: No such file or directory @ rb_sysopen - /assets/js/my.js in /github/workspace/_layouts/my.html
                    ------------------------------------------------
      Jekyll 4.1.1   Please append `--trace` to the `build` command 
                     for any additional information or backtrace. 
                    ------------------------------------------------
/github/workspace/_plugins/flexible_include.rb:140:in `abort': flexible_include.rb: No such file or directory @ rb_sysopen - /assets/js/my.js (SystemExit)
	from /github/workspace/_plugins/flexible_include.rb:140:in `rescue in render'
	from /github/workspace/_plugins/flexible_include.rb:135:in `render'

or...

   Liquid Exception: no implicit conversion of nil into String in /github/workspace/_layouts/my.html
                    ------------------------------------------------
      Jekyll 4.1.1   Please append `--trace` to the `build` command 
                     for any additional information or backtrace. 
                    ------------------------------------------------
/github/workspace/_plugins/flexible_include.rb:130:in `join': no implicit conversion of nil into String (TypeError)
	from /github/workspace/_plugins/flexible_include.rb:130:in `render'

What is wrong did I do?

[mslinn]

Possible reasons for this error message are:

• A directory called assets/js, based at the top of your Jekyll project, does not exist
• The directory exists but does not contain a file called my.js
• The directory and/or file lacks read permission.