jekyll: for error "invalid because it contains a colon", please specify which file has the error.

• [x ] I believe this to be a bug, not a question about using Jekyll.
• [ x] I Updated to the latest Jekyll (or) if on Github Pages to the latest github-pages
• [ x] I Read the CONTRIBUTION file at https://jekyllrb.com/docs/contributing/
• This is a feature request.

---

• I am on (or have tested on) _macOS_ 10+
• [ x] I am on (or have tested on) _Debian/Ubuntu_ GNU/Linux
• I am on (or have tested on) _Fedora_ GNU/Linux
• I am on (or have tested on) _Arch_ GNU/Linux
• I am on (or have tested on) _Other_ GNU/Linux
• I am on (or have tested on) _Windows_ 10+
• I was trying to install.
• There is a broken Plugin API.
• I had an error on Github Pages, and I have not tested locally.
• I had an error on Github Pages, and Github Support said it was a Jekyll Bug.
• I had an error on Github Pages and I did not test it locally.
• [x ] I was trying to build.
• It was another bug.

My Reproduction Steps

jekyll serve

I upgraded from 3.0.0 to 3.2.1 and now I’m getting an error I didn’t get before:

$ jekyll serve
Configuration file: none
            Source: /home/mark/Documents/personal/mark.stosberg.com/preview-site/_posts
       Destination: /home/mark/Documents/personal/mark.stosberg.com/preview-site/_posts/_site
 Incremental build: disabled. Enable with --incremental
      Generating... 
             ERROR: YOUR SITE COULD NOT BE BUILT:
                    ------------------------------------
                    The URL /:year/:month/:title.html is invalid because it contains a colon.

I’m happy to try to fix whatever the problem, but could please update the error to specify which file contains the problem so I don’t have to dig through them all? This error was not thrown with 3.0.0. It seems related to #5069.

The Output I Wanted