old_contents: # coding: utf-8
  
  import logging
  
  import flask
  
  from api import helpers
  import config
  
  from main import app
  
  
  @app.errorhandler(400)  # Bad Request
  @app.errorhandler(401)  # Unauthorized
  @app.errorhandler(403)  # Forbidden
  @app.errorhandler(404)  # Not Found
  @app.errorhandler(405)  # Method Not Allowed
  @app.errorhandler(410)  # Gone
  @app.errorhandler(418)  # I'm a Teapot
  @app.errorhandler(422)  # Unprocessable Entity
  @app.errorhandler(500)  # Internal Server Error
  def error_handler(e):
    try:
      e.code
    except AttributeError:
      e.code = 500
      e.name = 'Internal Server Error'
  
    logging.error('%d - %s: %s', e.code, e.name, flask.request.url)
    if e.code != 404:
      logging.exception(e)
  
    if flask.request.path.startswith('/api/'):
      return helpers.handle_error(e)
  
    return flask.render_template(
      'error.html',
      title='Error %d (%s)!!1' % (e.code, e.name),
      html_class='error-page',
      error=e,
    ), e.code
  
  
  if config.PRODUCTION:
    @app.errorhandler(Exception)
    def production_error_handler(e):
      return error_handler(e)
  
new_contents: # coding: utf-8
  
  import logging
  
  import flask
  import werkzeug
  
  from api import helpers
  import config
  
  from main import app
  
  
  @app.errorhandler(400)  # Bad Request
  @app.errorhandler(401)  # Unauthorized
  @app.errorhandler(403)  # Forbidden
  @app.errorhandler(404)  # Not Found
  @app.errorhandler(405)  # Method Not Allowed
  @app.errorhandler(410)  # Gone
  @app.errorhandler(418)  # I'm a Teapot
  @app.errorhandler(422)  # Unprocessable Entity
  @app.errorhandler(500)  # Internal Server Error
  def error_handler(e):
    try:
      e.code
    except AttributeError:
      e.code = 500
      e.name = 'Internal Server Error'
  
    logging.error('%d - %s: %s', e.code, e.name, flask.request.url)
    if e.code != 404:
      logging.exception(e)
  
    if flask.request.path.startswith('/api/'):
      return helpers.handle_error(e)
  
    return flask.render_template(
      'error.html',
      title='Error %d (%s)!!1' % (e.code, e.name),
      html_class='error-page',
      error=e,
    ), e.code
  
  
  if config.PRODUCTION:
    @app.errorhandler(Exception)
    def production_error_handler(e):
      if isinstance(e, werkzeug.exceptions.HTTPException) and e.code in (301, 302):
        return e
      return error_handler(e)
  
subject: Fix and close #878 (#935)