Fixed eslint errors & improved a lot of error handling

src/cache/redis.js

@@ -3,29 +3,29 @@ const configuration = require("../config/configuration").getInstance();
 let client;
 
 try {
-  const redis = require("redis");
-  console.log("Trying to connect with redis..");
+  const redis = require("redis"); // eslint-disable-line global-require
+  console.log("Trying to connect with redis.."); // eslint-disable-line no-console
   const host = configuration.get("redis", "host");
   const port = configuration.get("redis", "port");
 
-  console.log(`redis://${host}:${port}`);
+  console.log(`redis://${host}:${port}`); // eslint-disable-line no-console
   client = redis.createClient({
     url: `redis://${host}:${port}`
   });
 
-  client.on("connect", () => console.log("Redis connection established!"));
+  client.on("connect", () => console.log("Redis connection established!")); // eslint-disable-line no-console
 
   client.on("error", () => {
     client.quit();
-    console.error("Unable to connect to redis, setting up redis-mock.");
+    console.error("Unable to connect to redis, setting up redis-mock."); // eslint-disable-line no-console
 
     client = {
-      get() {
-        console.log("redis-dummy get", arguments[0]);
+      get(command) {
+        console.log(`redis-dummy get: ${command}`); // eslint-disable-line no-console
         return Promise.resolve();
       },
-      set() {
-        console.log("redis-dummy set", arguments[0]);
+      set(command) {
+        console.log(`redis-dummy set: ${command}`); // eslint-disable-line no-console
         return Promise.resolve();
       }
     };
@@ -41,6 +41,7 @@ function set(key, value, TTL = 10800) {
       // successfully set value with key, now set TTL for key
       client.expire(key, TTL, e => {
         if (e)
+          // eslint-disable-next-line no-console
           console.error(
             "Unexpected error while setting expiration for key:",
             key,