Added this in the Docker file before npm install:

RUN apk add --update python make g++\
   && rm -rf /var/cache/apk/*

This was to fix this error "gyp ERR! find Python":
> sleep@6.3.0 install /app/node_modules/sleep
> node-gyp rebuild
gyp ERR! find Python

Dockerfile

@@ -4,6 +4,8 @@ RUN mkdir -p /app
 WORKDIR /app
 COPY package.json /app
 
+RUN apk add --update python make g++\
+   && rm -rf /var/cache/apk/*
 
 
 RUN npm install