Google Authorization

Step 1: Create a service account

Open Google Developers Console.
If you already have a project, use the drop-down to select a project. If you don't have a project listed or want to create a new one, click Create project.
Select the Menu icon Menu icon > Permissions > Service accounts > Create service account.
Follow the on-screen instructions and select Create.
Copy the email address listed.
    Example: accountName@project.iam.gserviceaccount.com
Please note that new service account may take up to 24 hours to work.

Step 2: Add the service account on Play Console

Open Play Console.
Select Settings Settings > User accounts & rights > Invite new user.
Paste or type the email address associated with your service account.
Based on the types of reports needed, select permissions. 
    Tip: Read the Add developer account users and manage permissions article to understand the different access levels users have and the rights that different permissions grant them.
Click Add user. Your service account will be added to your account.

Step 3: Replace private_key.json with your private_key.json

Download json file of your service account. (The one you created in step 1)
Copy text from the downloaded file and paste it into private_key.json file available in project root directory.

Google cloud storage bucket details

You can copy your Google Cloud Storage URI by following below steps:

Sign in to your google play console.
Expand download reports section from the menu on the left. (make sure you are not inside the app)
Click your desired report section and your find button "Copy cloud storage URI".
Your Cloud Storage URI begins with pubsite_prod_rev (e.g., pubsite_prod_rev_01234567890987654321).

For files/paths inside bucket, please see "Commands and file formats for detailed reports" section by clicking this link https://support.google.com/googleplay/android-developer/answer/6135870