Bug with SQLite as backend

[springcoil]

I've come across this bug. I'm trying to reproduce the bioassay_model - and pass that to the backend.

Has something changed with backend trace?

ProgrammingError                          Traceback (most recent call last)
<ipython-input-32-9f8ba87a6c6a> in <module>()
      1 with bioassay_model:
----> 2     db_trace = pm.sample(100, trace='sqlite')

~/miniconda3/envs/stat-rethink-pymc3/lib/python3.6/site-packages/pymc3/sampling.py in sample(draws, step, init, n_init, start, trace, chain_idx, chains, cores, tune, nuts_kwargs, step_kwargs, progressbar, model, random_seed, live_plot, discard_tuned_samples, live_plot_kwargs, compute_convergence_checks, use_mmap, **kwargs)
    447             _print_step_hierarchy(step)
    448             try:
--> 449                 trace = _mp_sample(**sample_args)
    450             except pickle.PickleError:
    451                 _log.warning("Could not pickle model, sampling singlethreaded.")

~/miniconda3/envs/stat-rethink-pymc3/lib/python3.6/site-packages/pymc3/sampling.py in _mp_sample(draws, tune, step, chains, cores, chain, random_seed, start, progressbar, trace, model, use_mmap, **kwargs)
   1013         finally:
   1014             for trace in traces:
-> 1015                 trace.close()
   1016 
   1017     else:

~/miniconda3/envs/stat-rethink-pymc3/lib/python3.6/site-packages/pymc3/backends/sqlite.py in close(self)
    165 
    166     def close(self):
--> 167         self._execute_queue()
    168         self.db.close()
    169 

~/miniconda3/envs/stat-rethink-pymc3/lib/python3.6/site-packages/pymc3/backends/sqlite.py in _execute_queue(self)
    162                 self.db.cursor.executemany(self.var_inserts[varname],
    163                                            self._queue[varname])
--> 164                 self._queue[varname] = []
    165 
    166     def close(self):

ProgrammingError: Cannot operate on a closed database.```