docs: def search_carts(env, pkg_name, repos):
      """
      returns a list of carts containing a package with the specified name
  
      env: the name of an environment from the juicer config
      pkg_name: the name of the package for which to search
      repos: a list of repos in which to search for the package
      """
      db = cart_db()
      carts = db[env]
  
      for repo in repos:
          field = 'repos_items.%s' % repo
          value = '.*%s.*' % pkg_name
  
          found_carts = []
  
          for cart in carts.find({field: {'$regex': value}}):
              found_carts.append(cart)
          return found_carts