old_contents: from flask import g
  from flask.ext.login import current_user
  
  from tmi.core import app
  from tmi.assets import assets # noqa
  from tmi.views.ui import ui # noqa
  from tmi.views.auth import login, logout # noqa
  from tmi.views.admin import admin # noqa
  from tmi.views.cards_api import blueprint as cards_api
  
  
  @app.before_request
  def before_request():
      g.user = current_user
  
  app.register_blueprint(cards_api)
  
new_contents: from flask import g, request
  from flask.ext.login import current_user
  from werkzeug.exceptions import HTTPException
  
  from tmi.core import app
  from tmi.forms import Invalid
  from tmi.util import jsonify
  from tmi.assets import assets # noqa
  from tmi.views.ui import ui # noqa
  from tmi.views.auth import login, logout # noqa
  from tmi.views.admin import admin # noqa
  from tmi.views.cards_api import blueprint as cards_api
  
  
  @app.before_request
  def before_request():
      g.user = current_user
  
  app.register_blueprint(cards_api)
  
  
  @app.errorhandler(401)
  @app.errorhandler(403)
  @app.errorhandler(404)
  @app.errorhandler(410)
  @app.errorhandler(500)
  def handle_exceptions(exc):
      if isinstance(exc, HTTPException):
          message = exc.get_description(request.environ)
          message = message.replace('<p>', '').replace('</p>', '')
          body = {
              'status': exc.code,
              'name': exc.name,
              'message': message
          }
          headers = exc.get_headers(request.environ)
      else:
          body = {
              'status': 500,
              'name': exc.__class__.__name__,
              'message': unicode(exc)
          }
          headers = {}
      return jsonify(body, status=body.get('status'),
                     headers=headers)
  
  
  @app.errorhandler(Invalid)
  def handle_invalid(exc):
      body = {
          'status': 400,
          'name': 'Invalid Data',
          'message': unicode(exc),
          'errors': exc.asdict()
      }
      return jsonify(body, status=400)
  
subject: Handle errors with JSON messages.