dual_annealing does not set the success attribute in OptimizeResult

[andyfaff]

from scipy.optimize import dual_annealing, rosen
res = dual_annealing(rosen, [(-2, 2), (-2, 2)])
print(res.success)

Gives:

--------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
~/miniconda3/envs/dev3/lib/python3.7/site-packages/scipy/optimize/optimize.py in __getattr__(self, name)
    113         try:
--> 114             return self[name]
    115         except KeyError:

KeyError: 'success'

During handling of the above exception, another exception occurred:

AttributeError                            Traceback (most recent call last)
<ipython-input-4-402eff86d4dd> in <module>
      1 from scipy.optimize import dual_annealing, rosen
      2 res = dual_annealing(rosen, [(-2, 2), (-2, 2)])
----> 3 res.success

~/miniconda3/envs/dev3/lib/python3.7/site-packages/scipy/optimize/optimize.py in __getattr__(self, name)
    114             return self[name]
    115         except KeyError:
--> 116             raise AttributeError(name)
    117 
    118     __setattr__ = dict.__setitem__

AttributeError: success