Why is there an error when starting jekyll?

Question

ruby

I recently decided to try jekyll. Here is the first problem that I had to face: when adding a font to a style file, an error pops up:

/home/dart/Sandbox/jekyll/julav/_sass/fonts'
Configuration file: none

Here is the _config.yml file

name: Your Name

description: Web Developer from Somewhere

avatar: https://raw.githubusercontent.com/barryclark/jekyll-now/master/images/jekyll-logo.png

footer-links:
  dribbble:
  email:
  facebook:
  flickr:
  github: barryclark/jekyll-now
  instagram:
  linkedin:
  pinterest:
  rss: # just type anything here for a working RSS icon
  twitter: jekyllrb
  stackoverflow: # your stackoverflow profile, e.g. "users/50476/bart-kiers"
  youtube: # channel/<your_long_string> or user/<user-name>
  googleplus: # anything in your profile username that comes after plus.google.com/

# Your website URL (e.g. http://barryclark.github.io or http://www.barryclark.co)
# Used for Sitemap.xml and your RSS feed
url:

baseurl: ""

permalink: /:title/

# The release of Jekyll Now that you're using
version: v1.2.0

# Jekyll 3 now only supports Kramdown for Markdown
kramdown:
  # Use GitHub flavored markdown, including triple backtick fenced code blocks
  input: GFM
  # Jekyll 3 and GitHub Pages now only support rouge for syntax highlighting
  syntax_highlighter: rouge
  syntax_highlighter_opts:
    # Use existing pygments syntax highlighting css
    css_class: 'highlight'

# Set the Sass partials directory, as we're using @imports
sass:
  style: :expanded # You might prefer to minify using :compressed

# Use the following plug-ins
gems:
  - jekyll-sitemap # Create a sitemap using the official Jekyll sitemap gem
  - jekyll-feed # Create an Atom feed using the official Jekyll feed gem

# Exclude these files from your production _site
exclude:
  - Gemfile
  - Gemfile.lock
  - LICENSE
  - README.md
  - CNAME

And here's how to include the file:

@font-face {
  font-family: RobotoMono;
  src: url('fonts/robotoMono/RobotoMono-Medium.ttf');
}