Raise execution error if solver did not finish normally

After normal completition solve status is one. Higher values indicate an error.

CHANGELOG.md

 # Changelog
 All notable changes to this project will be documented in this file.
 
+## Unreleased
+### Added
+- Raise execution error if solver did not finish normally
+
 ## 1.1.5
 ### Fixed
 - Long-term scenario data when using only one scenario

inc/3e_solve.gms

@@ -51,18 +51,22 @@ $offtext
         schedule.holdfixed = 1; // Enable holdfixed, which makes the GAMS compiler convert fixed variables into parameters for the solver.
         schedule.OptFile = 1;
         solve schedule using mip minimizing v_obj;
+        // Check solve status (1 = normal completion)
+        if(schedule.solveStat > 1, execError = execError + 1);
     ); // END IF SCHEDULE
 
     if (mSolve('building'),
         building.holdfixed = 1;
         building.OptFile = 1;
         solve building using mip minimizing v_obj;
+        if(building.solveStat > 1, execError = execError + 1);
     ); // END IF BUILDING
 
     if (mSolve('invest'),
         invest.holdfixed = 1; // Enable holdfixed, which makes the GAMS compiler convert fixed variables into parameters for the solver.
         invest.OptFile = 1;
         solve invest using mip minimizing v_obj;
+        if(invest.solveStat > 1, execError = execError + 1);
     ); // END IF INVEST