sage: from sage.numerical.backends.generic_backend import get_solver
sage: p = get_solver(solver = "GLPK") 
sage: p.add_variable()
1
sage: p.variable_upper_bound(1)
sig_error() without sig_on()
...
------------------------------------------------------------------------
Unhandled SIGABRT: An abort() occurred.
This probably occurred because a *compiled* module has a bug
in it and is not properly wrapped with sig_on(), sig_off().
Python will now terminate.
------------------------------------------------------------------------
Aborted