Improve error message "solver is not available" to indicate to check the bindings
While testing the example in the "installation" section of the documentation, I had the following error:
>>> P.solve(solver="glpk")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/gderval/miniconda3/lib/python3.8/site-packages/picos/modeling/problem.py", line 1784, in solve
self._strategy = Strategy.from_problem(
File "/home/gderval/miniconda3/lib/python3.8/site-packages/picos/modeling/strategy.py", line 186, in from_problem
raise RuntimeError(
RuntimeError: Selected solver GLPK is not available on the system.
In fact, GLPK was available on my system, but its python bindings (swiglpk) were not.
Adding a little message, either general "check that you installed the solver and its python bindings" or solver-specific "GLPK (or its python package swiglpk) is not available", or something like that may help new users.