Handle get request.

def get(self):
    """Handle get request."""
    client_customer_id = self.request.get('clientCustomerId')

    template_values = {
        'back_url': '/showAccounts',
        'back_msg': 'View Accounts.',
        'ccid': client_customer_id,
        'logout_url': users.create_logout_url('/'),
        'user_nickname': users.get_current_user().nickname()
    }

    try:
      try:
        app_user = InitUser()

        # Load Client instance.
        handler = APIHandler(app_user.client_id,
                             app_user.client_secret,
                             app_user.refresh_token,
                             app_user.adwords_manager_cid,
                             app_user.developer_token)

        campaigns = handler.GetCampaigns(client_customer_id)
      except Exception, e:
        template_values['error'] = str(e)
    finally:
      # Use template to write output to the page.
      template_values['campaigns'] = campaigns
      path = os.path.join(os.path.dirname(__file__),
                          '../templates/show_campaigns.html')
      self.response.out.write(template.render(path, template_values))