sage: Parallelism().set(nproc=2)                                                                    
sage: M = Manifold(2, 'M')                                                                          
sage: X.<x,y> = M.chart()                                                                           
sage: t = M.tensor_field(0, 2)                                                                      
sage: t[0,0], t[0,1], t[1,1] = function('f')(x), x+y, x-y                                           
sage: v = M.vector_field(1 + x*y, -x^2)                                                             
sage: s = t.contract(v)  # parallelized computation occurs here
---------------------------------------------------------------------------
RemoteTraceback                           Traceback (most recent call last)
RemoteTraceback: 
"""
Traceback (most recent call last):
  File "/home/eric/sage/9.3.develop/local/lib/python3.8/site-packages/sage/interfaces/interface.py", line 718, in __init__
    self._name = parent._create(value, name=name)
  File "/home/eric/sage/9.3.develop/local/lib/python3.8/site-packages/sage/interfaces/maxima_lib.py", line 604, in _create
    self.set(name, value)
...
  File "sage/libs/ecl.pyx", line 352, in sage.libs.ecl.ecl_safe_funcall (build/cythonized/sage/libs/ecl.c:5735)
    raise RuntimeError("ECL says: {}".format(
RuntimeError: ECL says: THROW: The catch MACSYMA-QUIT is undefined.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3.8/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "sage/misc/fpickle.pyx", line 104, in sage.misc.fpickle.call_pickled_function (build/cythonized/sage/misc/fpickle.c:2384)
    res = eval("f(*args, **kwds)",sage.all.__dict__, {'args':args, 'kwds':kwds, 'f':f})
  File "<string>", line 1, in <module>
  File "/home/eric/sage/9.2.develop/local/lib/python3.7/site-packages/sage/tensor/modules/comp.py", line 2329, in make_Contraction
    sm += this[[ind_s]] * other[[ind_o]]
...
 File "/home/eric/sage/9.3.develop/local/lib/python3.8/site-packages/sage/interfaces/interface.py", line 720, in __init__
    raise TypeError(x)
TypeError: ECL says: THROW: The catch MACSYMA-QUIT is undefined.
"""

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

TypeError                                 Traceback (most recent call last)
<ipython-input-9-d1a8f1c47ea1> in <module>
----> 1 s = t.contract(v)  # parallelized computation occurs here
...
/usr/lib/python3.8/multiprocessing/pool.py in next(self, timeout)
    866         if success:
    867             return value
--> 868         raise value
    869 
    870     __next__ = next                    # XXX

TypeError: ECL says: THROW: The catch MACSYMA-QUIT is undefined.