check _skip_trivial_costraints before the constraint body

Author: bknueven

Diff for: pyomo/solvers/plugins/solvers/gurobi_direct.py

@@ -493,9 +493,8 @@ def _add_constraint(self, con):
         if not con.active:
             return None
 
-        if is_fixed(con.body):
-            if self._skip_trivial_constraints:
-                return None
+        if self._skip_trivial_constraints and is_fixed(con.body):
+            return None
 
         conname = self._symbol_map.getSymbol(con, self._labeler)
 

Diff for: pyomo/solvers/plugins/solvers/xpress_direct.py

@@ -667,9 +667,8 @@ def _add_constraint(self, con):
         if not con.active:
             return None
 
-        if is_fixed(con.body):
-            if self._skip_trivial_constraints:
-                return None
+        if self._skip_trivial_constraints and is_fixed(con.body):
+            return None
 
         conname = self._symbol_map.getSymbol(con, self._labeler)