old_contents: # See https://zulip.readthedocs.io/en/latest/subsystems/thumbnailing.html
  from __future__ import absolute_import
  
  from six.moves import urllib
  from tornado.concurrent import return_future
  from thumbor.loaders import LoaderResult, file_loader, https_loader
  from tc_aws.loaders import s3_loader
  from thumbor.context import Context
  from .helpers import (
      separate_url_and_source_type,
      THUMBOR_S3_TYPE, THUMBOR_LOCAL_FILE_TYPE, THUMBOR_EXTERNAL_TYPE
  )
  
  from typing import Any, Callable
  
  import base64
  import logging
  
  def get_not_found_result():
      # type: () -> LoaderResult
      result = LoaderResult()
      result.error = LoaderResult.ERROR_NOT_FOUND
      result.successful = False
      return result
  
  @return_future
  def load(context, url, callback):
      # type: (Context, str, Callable[..., Any]) -> None
      source_type, encoded_url = separate_url_and_source_type(url)
      actual_url = base64.urlsafe_b64decode(urllib.parse.unquote(encoded_url))
      if source_type not in (THUMBOR_S3_TYPE, THUMBOR_LOCAL_FILE_TYPE,
                             THUMBOR_EXTERNAL_TYPE):
          callback(get_not_found_result())
          logging.warning('INVALID SOURCE TYPE: ' + source_type)
          return
  
      local_file_path_prefix = ''
      if actual_url.startswith('/user_uploads/'):  # type: ignore # python 2 type differs from python 3 type
          actual_url = actual_url[len('/user_uploads/'):]
          local_file_path_prefix = 'files/'
      elif actual_url.startswith('/user_avatars/'):  # type: ignore # python 2 type differs from python 3 type
          actual_url = actual_url[len('/user_avatars/'):]
          local_file_path_prefix = 'avatars/'
  
      if source_type == THUMBOR_S3_TYPE:
          s3_loader.load(context, actual_url, callback)
      elif source_type == THUMBOR_LOCAL_FILE_TYPE:
          patched_local_url = local_file_path_prefix + actual_url  # type: ignore # python 2 type differs from python 3 type
          file_loader.load(context, patched_local_url, callback)
      elif source_type == THUMBOR_EXTERNAL_TYPE:
          https_loader.load(context, actual_url, callback)
  
new_contents: # See https://zulip.readthedocs.io/en/latest/subsystems/thumbnailing.html
  from __future__ import absolute_import
  
  from six.moves import urllib
  from tornado.concurrent import return_future
  from thumbor.loaders import LoaderResult, file_loader, https_loader
  from tc_aws.loaders import s3_loader
  from thumbor.context import Context
  from .helpers import (
      separate_url_and_source_type,
      THUMBOR_S3_TYPE, THUMBOR_LOCAL_FILE_TYPE, THUMBOR_EXTERNAL_TYPE
  )
  
  from typing import Any, Callable
  
  import base64
  import logging
  
  def get_not_found_result():
      # type: () -> LoaderResult
      result = LoaderResult()
      result.error = LoaderResult.ERROR_NOT_FOUND
      result.successful = False
      return result
  
  @return_future
  def load(context, url, callback):
      # type: (Context, str, Callable[..., Any]) -> None
      source_type, encoded_url = separate_url_and_source_type(url)
      actual_url = base64.urlsafe_b64decode(urllib.parse.unquote(encoded_url))
      if source_type not in (THUMBOR_S3_TYPE, THUMBOR_LOCAL_FILE_TYPE,
                             THUMBOR_EXTERNAL_TYPE):
          callback(get_not_found_result())
          logging.warning('INVALID SOURCE TYPE: ' + source_type)
          return
  
      if source_type == THUMBOR_S3_TYPE:
          s3_loader.load(context, actual_url, callback)
      elif source_type == THUMBOR_LOCAL_FILE_TYPE:
          if actual_url.startswith('/user_uploads/'):  # type: ignore # python 2 type differs from python 3 type
              actual_url = actual_url[len('/user_uploads/'):]
              local_file_path_prefix = 'files/'
          elif actual_url.startswith('/user_avatars/'):  # type: ignore # python 2 type differs from python 3 type
              actual_url = actual_url[len('/user_avatars/'):]
              local_file_path_prefix = 'avatars/'
          else:
              raise AssertionError("Unexpected local file.")
  
          patched_local_url = local_file_path_prefix + actual_url  # type: ignore # python 2 type differs from python 3 type
          file_loader.load(context, patched_local_url, callback)
      elif source_type == THUMBOR_EXTERNAL_TYPE:
          https_loader.load(context, actual_url, callback)
  
subject: Make local_file_path logic more obvious.