Server: check the host key is not present in configurations

The parameter was renamed to hostname

server.js

@@ -26,9 +26,14 @@ database.connect()
 // ----------- Checker -----------
 const checker = require('./server/initializers/checker')
 
-const miss = checker.checkConfig()
+const missed = checker.checkMissedConfig()
-if (miss.length !== 0) {
+if (missed.length !== 0) {
-  throw new Error('Miss some configurations keys : ' + miss)
+  throw new Error('Miss some configurations keys : ' + missed)
+}
+
+const errorMessage = checker.checkConfig()
+if (errorMessage !== null) {
+  throw new Error(errorMessage)
 }
 
 // ----------- PeerTube modules -----------

server/initializers/checker.js

@@ -8,12 +8,25 @@ const User = mongoose.model('User')
 
 const checker = {
   checkConfig,
+  checkMissedConfig,
   clientsExist,
   usersExist
 }
 
-// Check the config files
+// Some checks on configuration files
 function checkConfig () {
+  if (config.has('webserver.host')) {
+    let errorMessage = '`host` config key was renamed to `hostname` but it seems you still have a `host` key in your configuration files!'
+    errorMessage += ' Please ensure to rename your `host` configuration to `hostname`.'
+
+    return errorMessage
+  }
+
+  return null
+}
+
+// Check the config files
+function checkMissedConfig () {
   const required = [ 'listen.port',
     'webserver.https', 'webserver.hostname', 'webserver.port',
     'database.hostname', 'database.port', 'database.suffix',