More informative OptimizerResult.message in case of exceptions

So far only the exception message was stored if an exception occurred
during optimization with FidesOptimizer. This is often enough not
helpful at all.
Now this includes exception type / message / traceback.

Related to #1147

pypesto/optimize/optimizer.py

@@ -1337,8 +1337,11 @@ def minimize(
         try:
             opt.minimize(x0)
             msg = self._convert_exitflag_to_message(opt)
-        except RuntimeError as err:
-            msg = str(err)
+        except RuntimeError:
+            import sys
+            import traceback
+
+            msg = "\n".join(traceback.format_exception(*sys.exc_info()))
 
         optimizer_result = OptimizerResult(
             x=opt.x_min,