code: def create_credentials(credentials_file=None,
                         service_email=None,
                         service_key=None,
                         scope='https://www.googleapis.com/auth/androidpublisher'):
      
      credentials = None
      if service_email is None and service_key is None:
          print(credentials_file)
          if credentials_file is None:
              # try load file from env
              key = 'PLAY_DELIVER_CREDENTIALS'
              if key in os.environ:
                  credentials_file = os.environ[key]
  
          if credentials_file is None:
              # try to find the file in home
              path = os.path.expanduser('~/.playdeliver/credentials.json')
              if os.path.exists(path):
                  credentials_file = path
  
          if credentials_file is not None:
              credentials = client.GoogleCredentials.from_stream(
                  credentials_file)
              credentials = credentials.create_scoped(scope)
          else:
              sys.exit("no credentials")
      else:
          credentials = client.SignedJwtAssertionCredentials(
              service_email, _load_key(service_key), scope=scope)
      return credentials
docs: Create Google credentials object.
  
      If given credentials_file is None, try to retrieve file path from environment 
      or look up file in homefolder.