Fix build problem

eslint and node incompatebility

.travis.yml

@@ -18,6 +18,17 @@ install:
 - pip install coverage  # for code coverage
 - pip install -r monkey/infection_monkey/requirements.txt  # for unit tests
 
+# node + npm + eslint
+- node --version
+- npm --version
+# Install NVM, see https://github.com/nvm-sh/nvm#installing-and-updating
+- curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | bash
+- nvm install node
+- nvm use node
+- npm i -g eslint
+- node --version
+- npm --version
+
 before_script:
 # Set the server config to `testing`. This is required for for the UTs to pass.
 - python monkey/monkey_island/cc/set_server_config.py testing
@@ -49,12 +60,9 @@ script:
 # Check JS code. The npm install must happen AFTER the flake8 because the node_modules folder will cause a lot of errors.
 - cd monkey_island/cc/ui
 - npm i
-- npm i -g eslint
-- cd -
-- cd monkey_island/cc/ui
-- eslint ./src --quiet
+- eslint ./src --quiet  # Test for errors
 - JS_WARNINGS_AMOUNT_UPPER_LIMIT=490
-- eslint ./src --max-warnings $JS_WARNINGS_AMOUNT_UPPER_LIMIT
+- eslint ./src --max-warnings $JS_WARNINGS_AMOUNT_UPPER_LIMIT  # Test for max warnings
 
 after_success:
   # Upload code coverage results to codecov.io, see https://github.com/codecov/codecov-bash for more information