TypeError: 'JsonObject' object is unsubscriptable when pagenotfound should be generated

I get this ugly "Internal Server Error" when I should be getting a neat 'page not found' page when an internal Pylons:python error occurs.

I have simulated a Python error elsewhere & the correct pagenotfound template is generated. In my config (development.ini): debug = false, full_stack = true ... so as to render this page when an exception occurs.

This is how the middleware.py looks currently:

"""Pylons middleware initialization"""
from beaker.middleware import CacheMiddleware, SessionMiddleware
from paste.cascade import Cascade
from paste.registry import RegistryManager
from paste.urlparser import StaticURLParser
from paste.deploy.converters import asbool
from pylons import config
from pylons.middleware import ErrorHandler, StatusCodeRedirect
from observer import Observer
from pylons.wsgiapp import PylonsApp
from routes.middleware import RoutesMiddleware
from r4l.lib.components.middleware.striptrailingslash import     StripTrailingSlash
from r4l.config.environment import load_environment

def make_app(global_conf, full_stack=True, static_files=True, **app_conf):
"""
Create a Pylons WSGI application and return it

``global_conf``
    The inherited configuration for this application. Normally from
    the [DEFAULT] section of the Paste ini file.

``full_stack``
    Whether this application provides a full WSGI stack (by default,
    meaning it handles its own exceptions and errors). Disable
    full_stack when this application is "managed" by another WSGI
    middleware.

``static_files``
    Whether this application serves its own static files; disable
    when another web server is responsible for serving them.

``app_conf``
    The application's local configuration. Normally specified in
    the [app:<name>] section of the Paste ini file (where <name>
    defaults to main).

"""
# Configure the Pylons environment
load_environment(global_conf, app_conf)

# The Pylons WSGI app
app = PylonsApp()

# Routing/Session/Cache Middleware
app = RoutesMiddleware(app, config['routes.map'])
app = SessionMiddleware(app, config)
app = CacheMiddleware(app, config)

# CUSTOM MIDDLEWARE HERE (filtered by error handling middlewares)

if asbool(full_stack):
    # Handle Python exceptions
    app = ErrorHandler(app, global_conf, **config['pylons.errorware'])
    app = Observer(app)

    # Display error documents for 401, 403, 404 status codes (and
    # 500 when debug is disabled)
    if asbool(config['debug']):
        app = StatusCodeRedirect(app, [400, 401, 403, 404], '/content/pagenotfound')
    else:
        app = StatusCodeRedirect(app, [400, 401, 403, 404, 500], '/content/pagenotfound')

# Establish the Registry for this application
app = RegistryManager(app)

if asbool(static_files):
    # Serve static files
    static_app = StaticURLParser(config['pylons.paths']['static_files'])
    app = Casca开发者_运维知识库de([static_app, app])

app = StripTrailingSlash(app)
return app

Also Observer.py class

from pylons.util import call_wsgi_application
from webob import Request, Response
from weberror import formatter, collector

class Observer(object):
""" Observer object to monitor and extract the traceback for 'pagenotfound' emails """

def __init__(self, app):
    self.app = app

def __call__(self, environ, start_response):        
    status, headers, app_iter, exc_info = call_wsgi_application(
        self.app, environ, catch_exc_info=True)
    if exc_info is not None:
        exc_data = collector.collect_exception(*exc_info)
        err_report = formatter.format_text(exc_data, show_hidden_frames=True)[0]
        environ['err_report'] = err_report
    start_response(status, headers, exc_info)
    return app_iter

this is the Error.py

import cgi

from paste.urlparser import PkgResourcesParser
from pylons import request
from pylons.controllers.util import forward
from pylons.middleware import error_document_template
from webhelpers.html.builder import literal

from r4l.lib.base import BaseController
from r4l.lib import helpers as h

class ErrorController(BaseController):

"""Generates error documents as and when they are required.

The ErrorDocuments middleware forwards to ErrorController when error
related status codes are returned from the application.

This behaviour can be altered by changing the parameters to the
ErrorDocuments middleware in your config/middleware.py file.

"""

def document(self):
    """Render the error document"""
    resp = request.environ.get('pylons.original_response')
    if resp.status_int == 404:
        h.redirect_to('/content/pagenotfound')
    content = literal(resp.body) or cgi.escape(request.GET.get('message', ''))
    page = error_document_template % \
        dict(prefix=request.environ.get('SCRIPT_NAME', ''),
             code=cgi.escape(request.GET.get('code', str(resp.status_int))),
             message=content)
    return page

def img(self, id):
    """Serve Pylons' stock images"""
    return self._serve_file('/'.join(['media/img', id]))

def style(self, id):
    """Serve Pylons' stock stylesheets"""
    return self._serve_file('/'.join(['media/style', id]))

def _serve_file(self, path):
    """Call Paste's FileApp (a WSGI application) to serve the file
    at the specified path
    """
    request.environ['PATH_INFO'] = '/%s' % path
    return forward(PkgResourcesParser('pylons', 'pylons'))

And finally the controller for pagenotfound func

@h.template(u'content/404')
def pagenotfound(self):
    """
    Default pagenotfound page
    """

    c.err_report = str(request.environ.get('pylons.original_response','')) + '\n\n'
    if 'err_report' in request.environ:
        c.err_report += request.environ.get('err_report','')
        log.info("###### c.err_report: %s" % c.err_report)
    c.page_title = u'Page Not Found'
    c.previous_url = request.environ.get('HTTP_REFERER', h.url_for('/'))
    pagenotfound = True
    session['pagenotfound'] = pagenotfound
    session.save()
    if c.login:
        user = Session.query(User).get(session[u'username'])
        if user:
            c.login.email = user.contactemail.value

This is the exception that is not being caught:

File '/home/chilton/work/cj2/CJ-7519/r4l/templates/resume/preview.html', line 441 in

${h.cj_month_year(employment.startdate)} - Current${employment.enddate.strftime('%m/%Y')}

ValueError: year=200 is before 1900; the datetime strftime() methods require year >= 1900

I've tried looking at different ways of solving this one, but without success.