Hi all, I deployed my experiment in Heroku, but I got some unexpected errors. 
It seems like the creation of on var 'des' in the player field fails, but the app runs well in my local env. 

```
Failed to create session: (raised as a result of Query-invoked autoflush; consider using a session.no_autoflush block if this flush is occurring prematurely) (psycopg2.errors.UndefinedColumn) column "des" of relation "dyna_img_player" does not exist LINE 1: ... _payoff, round_number, _role, eval, chosen_file, des, subse... ^ [SQL: INSERT INTO dyna_img_player (id_in_group, _payoff, round_number, _role, eval, chosen_file, des, subsession_id, group_id, participant_id, session_id) VALUES (%(id_in_group)s, %(_payoff)s, %(round_number)s, %(_role)s, %(eval)s, %(chosen_file)s, %(des)s, %(subsession_id)s, %(group_id)s, %(participant_id)s, %(session_id)s) RETURNING dyna_img_player.id] [parameters: {'id_in_group': 1, '_payoff': '0', 'round_number': 1, '_role': '', 'eval': None, 'chosen_file': None, 'des': None, 'subsession_id': 7, 'group_id': 7, 'participant_id': 7, 'session_id': 3}] (Background on this error at: http://sqlalche.me/e/13/f405)
Traceback (most recent call last):
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1276, in _execute_context
    self.dialect.do_execute(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 609, in do_execute
    cursor.execute(statement, parameters)
psycopg2.errors.UndefinedColumn: column "des" of relation "dyna_img_player" does not exist
LINE 1: ... _payoff, round_number, _role, eval, chosen_file, des, subse...
                                                             ^


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/app/.heroku/python/lib/python3.9/site-packages/otree/session.py", line 447, in create_session_traceback_wrapper
    return create_session(**kwargs)
  File "/app/.heroku/python/lib/python3.9/site-packages/otree/session.py", line 410, in create_session
    dbq(Participant).filter_by(session=session).update(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/query.py", line 4063, in update
    update_op.exec_()
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 1695, in exec_
    self._do_pre()
  File "", line 1, in 
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 1741, in _do_pre
    session._autoflush()
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 1633, in _autoflush
    util.raise_(e, with_traceback=sys.exc_info()[2])
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 182, in raise_
    raise exception
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 1622, in _autoflush
    self.flush()
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 2540, in flush
    self._flush(objects)
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 2682, in _flush
    transaction.rollback(_capture_exception=True)
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/util/langhelpers.py", line 68, in __exit__
    compat.raise_(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 182, in raise_
    raise exception
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/session.py", line 2642, in _flush
    flush_context.execute()
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/unitofwork.py", line 422, in execute
    rec.execute(self)
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/unitofwork.py", line 586, in execute
    persistence.save_obj(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 239, in save_obj
    _emit_insert_statements(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/orm/persistence.py", line 1135, in _emit_insert_statements
    result = cached_connections[connection].execute(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1011, in execute
    return meth(self, multiparams, params)
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/sql/elements.py", line 298, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1124, in _execute_clauseelement
    ret = self._execute_context(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1316, in _execute_context
    self._handle_dbapi_exception(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1510, in _handle_dbapi_exception
    util.raise_(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 182, in raise_
    raise exception
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1276, in _execute_context
    self.dialect.do_execute(
  File "/app/.heroku/python/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 609, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.ProgrammingError: (raised as a result of Query-invoked autoflush; consider using a session.no_autoflush block if this flush is occurring prematurely)
(psycopg2.errors.UndefinedColumn) column "des" of relation "dyna_img_player" does not exist
LINE 1: ... _payoff, round_number, _role, eval, chosen_file, des, subse...
                                                             
[SQL: INSERT INTO dyna_img_player (id_in_group, _payoff, round_number, _role, eval, chosen_file, des, subsession_id, group_id, participant_id, session_id) VALUES (%(id_in_group)s, %(_payoff)s, %(round_number)s, %(_role)s, %(eval)s, %(chosen_file)s, %(des)s, %(subsession_id)s, %(group_id)s, %(participant_id)s, %(session_id)s) RETURNING dyna_img_player.id]
[parameters: {'id_in_group': 1, '_payoff': '0', 'round_number': 1, '_role': '', 'eval': None, 'chosen_file': None, 'des': None, 'subsession_id': 7, 'group_id': 7, 'participant_id': 7, 'session_id': 3}]
(Background on this error at: http://sqlalche.me/e/13/f405)
```

Try resetting the database.

It works! Thank you so much Chris