Jekyll:dev would not install

I’ve hit a problem while installing npm on an iMac. It installed up to " jekyll:dev", but then says, repeatedly: “Dependency Error: Yikes” re pygments. the complete error message is below.

I’m over my head here. Can anyone help?
Rick


Running “jekyll:dev” (jekyll) task
jekyll build --source website --destination _site --config /var/folders/5c/dr5866qj0l3352m4j6v0s1bw0000gx/T/_config.21883F9k1dVdXu8A1.yml false local was initiated.

Configuration file: /var/folders/5c/dr5866qj0l3352m4j6v0s1bw0000gx/T/_config.21883F9k1dVdXu8A1.yml
Deprecation: Auto-regeneration can no longer be set from your configuration file(s). Use the --[no-]watch/-w command-line option instead.
Deprecation: The ‘pygments’ configuration option has been renamed to ‘highlighter’. Please update your config file accordingly. The allowed values are ‘rouge’, ‘pygments’ or null.
Source: website
Destination: _site
Incremental build: disabled. Enable with --incremental
Generating…
Dependency Error: Yikes! It looks like you don’t have pygments or one of its dependencies installed. In order to use Jekyll as currently configured, you’ll need to install this gem. The full error message from Ruby is: ‘cannot load such file – pygments’ If you run into trouble, you can find helpful resources at https://jekyllrb.com/help/!
Liquid Exception: pygments in documentation.md
ERROR: YOUR SITE COULD NOT BE BUILT:
------------------------------------
pygments
Warning: Deprecation: Auto-regeneration can no longer be set from your configuration file(s). Use the --[no-]watch/-w command-line option instead.
Deprecation: The ‘pygments’ configuration option has been renamed to ‘highlighter’. Please update your config file accordingly. The allowed values are ‘rouge’, ‘pygments’ or null.
Dependency Error: Yikes! It looks like you don’t have pygments or one of its dependencies installed. In order to use Jekyll as currently configured, you’ll need to install this gem. The full error message from Ruby is: ‘cannot load such file – pygments’ If you run into trouble, you can find helpful resources at https://jekyllrb.com/help/!
Liquid Exception: pygments in documentation.md
ERROR: YOUR SITE COULD NOT BE BUILT:
------------------------------------
pygments Use --force to continue.

Aborted due to warnings.