Fails when used in travis as dependency

[markusa]

Dear all,

below you find a minimal travis configuration file which stops travis from further continue the make command. It stops with:
The command "sudo npm install -g markdown-spellcheck" failed and exited with 1 during .

.travis.yml:

dist: focal
before_install:
 - sudo apt-get update
install: 
 - sudo apt-get install npm
 - sudo apt-get install hunspell hunspell-en-us
 - sudo npm install -g markdown-spellcheck
script: make

Any ideas how to fix this?