KeyError: 'oauth_state'

[arms203]

Hi I currently having an error on the master server site. The error log is

Traceback (most recent call last):
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1997, in call
return self.wsgi_app(environ, start_response)
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1985, in wsgi_app
response = self.handle_exception(e)
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1540, in handle_exception
reraise(exc_type, exc_value, tb)
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1982, in wsgi_app
response = self.full_dispatch_request()
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1614, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1517, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1612, in full_dispatch_request
rv = self.dispatch_request()
File "/home/arms/.local/lib/python2.7/site-packages/flask/app.py", line 1598, in dispatch_request
return self.view_functionsrule.endpoint
File "/home/arms/Project/whereareyou/app.py", line 112, in callback
google = get_google_auth(state=session['oauth_state'])
File "/home/arms/.local/lib/python2.7/site-packages/werkzeug/local.py", line 377, in
getitem = lambda x, i: x._get_current_object()[i]
KeyError: 'oauth_state'

Please help. Thank you.