GraphicsMagick is already installed in the image.

3 jobs for master in 34 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
failed #44668
book

00:00:34

failed #44667
build

00:00:34

 
  Deploy
skipped #44669
pages
 
Name Stage Failure
failed
book Build There is an unknown failure, please try again

An error occurred while installing prawn-gmagick (0.0.9), and Bundler cannot
continue.
Make sure that `gem install prawn-gmagick -v '0.0.9' --source
'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
prawn-gmagick
ERROR: Job failed: exit code 1
failed
build Build There is an unknown failure, please try again

An error occurred while installing prawn-gmagick (0.0.9), and Bundler cannot
continue.
Make sure that `gem install prawn-gmagick -v '0.0.9' --source
'https://rubygems.org/'` succeeds before bundling.

In Gemfile:
prawn-gmagick
ERROR: Job failed: exit code 1