Hypothesis:
I think it's because multiple processes try to read that file at the same time

Stacktrace
Thu Apr 18 01:28:35 2013] [error] Apr-18 01:28:35 ERROR Exception on /cohorts/test2/threshold [GET]
[Thu Apr 18 01:28:35 2013] [error] Traceback (most recent call last):
[Thu Apr 18 01:28:35 2013] [error] File "/usr/lib/python2.7/dist-packages/flask/app.py", line 1504, in wsgi_app
[Thu Apr 18 01:28:35 2013] [error] response = self.full_dispatch_request()
[Thu Apr 18 01:28:35 2013] [error] File "/usr/lib/python2.7/dist-packages/flask/app.py", line 1264, in full_dispatch_request
[Thu Apr 18 01:28:35 2013] [error] rv = self.handle_user_exception(e)
[Thu Apr 18 01:28:35 2013] [error] File "/usr/lib/python2.7/dist-packages/flask/app.py", line 1262, in full_dispatch_request
[Thu Apr 18 01:28:35 2013] [error] rv = self.dispatch_request()
[Thu Apr 18 01:28:35 2013] [error] File "/usr/lib/python2.7/dist-packages/flask/app.py", line 1248, in dispatch_request
[Thu Apr 18 01:28:35 2013] [error] return self.view_functions[rule.endpoint](req.view_args)
[Thu Apr 18 01:28:35 2013] [error] File "/usr/lib/python2.7/dist-packages/flask_login.py", line 485, in decorated_view
[Thu Apr 18 01:28:35 2013] [error] return fn(*args, kwargs)
[Thu Apr 18 01:28:35 2013] [error] File "/a/e3/E3Analysis/user_metrics/api/views.py", line 239, in output
[Thu Apr 18 01:28:35 2013] [error] data = get_data(rm)
[Thu Apr 18 01:28:35 2013] [error] File "/a/e3/E3Analysis/user_metrics/api/engine/data.py", line 125, in get_data
[Thu Apr 18 01:28:35 2013] [error] hash_table_ref = read_pickle_data()
[Thu Apr 18 01:28:35 2013] [error] File "/a/e3/E3Analysis/user_metrics/api/engine/data.py", line 259, in read_pickle_data
[Thu Apr 18 01:28:35 2013] [error] return cPickle.load(pkl_file)
[Thu Apr 18 01:28:35 2013] [error] ValueError: insecure string pickle

Version: unspecified
Severity: normal