old_contents: from django import template
  from longclaw import settings
  
  register = template.Library()
  
  @register.inclusion_tag("core/script.html")
  def longclaw_vendors_bundle():
      return {'path': 'core/js/vendors.bundle.js'}
  
  @register.inclusion_tag("core/script.html")
  def longclaw_client_bundle():
      return {'path': 'core/js/longclawclient.bundle.js'}
  
  @register.simple_tag
  def longclaw_api_url_prefix():
      return settings.API_URL_PREFIX
  
new_contents: import os
  from django import template
  from longclaw import settings
  
  register = template.Library()
  
  CLIENT_PATH = os.path.join('core', 'js', 'longclawclient.bundle.js')
  VENDORS_PATH = os.path.join('core', 'js', 'vendors.bundle.js')
  
  @register.inclusion_tag("core/script.html")
  def longclaw_vendors_bundle():
      assert os.path.exists(
          os.path.join(os.path.dirname(os.path.dirname(__file__)), 'static', VENDORS_PATH)
      )
      return {'path': VENDORS_PATH}
  
  @register.inclusion_tag("core/script.html")
  def longclaw_client_bundle():
      assert os.path.exists(
          os.path.join(os.path.dirname(os.path.dirname(__file__)), 'static', CLIENT_PATH)
      )
      return {'path': CLIENT_PATH}
  
  @register.simple_tag
  def longclaw_api_url_prefix():
      return settings.API_URL_PREFIX
  
  
  
subject: Add explicit checks for existence of JS. Fixes #165