node8: require nodejs >= 8.9.0, npm >= 6.4

Next version will be Etherpad 1.8. As planned in #3424, we are going to require
NodeJS >=8.9.0 and npm >= 6.4.

This commit implements that change and updates documentation and scripts.
Subsequent changes will get rid of old idioms, dating back to node < 0.7, that
still survive in the code.
Once migrated to NodeJS 8, we will be able to start working on migrating the
code base from callbacks to async/await, greatly simplifying legibility (see
#3540).

Closes #3557

README.md

@@ -9,7 +9,7 @@ Etherpad is a really-real time collaborative editor scalable to thousands of sim
 # Installation
 
 ## Requirements
-- `nodejs` >= **6.9.0** (preferred: `nodejs` >= **8.9**)
+- `nodejs` >= **8.9.0**
 
 ## Uber-Quick Ubuntu
 ```
@@ -19,7 +19,7 @@ git clone --branch master https://github.com/ether/etherpad-lite.git && cd ether
 ```
 
 ## GNU/Linux and other UNIX-like systems
-You'll need git and [node.js](https://nodejs.org) installed (minimum required Node version: **6.9.0**, preferred: >= **8.9**).
+You'll need git and [node.js](https://nodejs.org) installed (minimum required Node version: **8.9.0**).
 
 **As any user (we recommend creating a separate user called etherpad):**
 

bin/installDeps.sh

@@ -1,12 +1,12 @@
 #!/bin/sh
 
 # minimum required node version
-REQUIRED_NODE_MAJOR=6
+REQUIRED_NODE_MAJOR=8
 REQUIRED_NODE_MINOR=9
 
 # minimum required npm version
-REQUIRED_NPM_MAJOR=3
-REQUIRED_NPM_MINOR=10
+REQUIRED_NPM_MAJOR=6
+REQUIRED_NPM_MINOR=4
 
 require_minimal_version() {
   PROGRAM_LABEL="$1"

doc/plugins.md

@@ -115,7 +115,7 @@ Your plugin must also contain a [package definition file](https://docs.npmjs.com
   "author": "USERNAME (REAL NAME) <MAIL@EXAMPLE.COM>",
   "contributors": [],
   "dependencies": {"MODULE": "0.3.20"},
-  "engines": { "node": ">= 6.9.0"}
+  "engines": { "node": ">= 8.9.0"}
 }
 ```
 

src/node/server.js

@@ -32,12 +32,14 @@ log4js.replaceConsole();
  * early check for version compatibility before calling
  * any modules that require newer versions of NodeJS
  */
-NodeVersion.enforceMinNodeVersion('6.9.0');
+NodeVersion.enforceMinNodeVersion('8.9.0');
 
 /*
- * Since Etherpad 1.8.0, at least NodeJS 8.9.0 will be required
+ * As of Etherpad 1.8.0, we do not have any further Node version deprecation in
+ * place.
+ *
+ * NodeVersion.checkDeprecationStatus('10.13.0', '1.9.0');
  */
-NodeVersion.checkDeprecationStatus('8.9.0', '1.8.0');
 
 /*
  * start up stats counting system

src/package.json

@@ -73,8 +73,8 @@
     "wd": "1.11.1"
   },
   "engines": {
-    "node": ">=6.9.0",
-    "npm": ">=3.10.8"
+    "node": ">=8.9.0",
+    "npm": ">=6.4.1"
   },
   "repository": {
     "type": "git",