Don't print expressions inside error()

src/main/scala/leon/synthesis/Solution.scala

@@ -96,6 +96,6 @@ object Solution {
 
   def UNSAT(implicit p: Problem): Solution = {
     val tpe = tupleTypeWrap(p.xs.map(_.getType))
-    Solution(BooleanLiteral(false), Set(), Error(tpe, p.phi+" is UNSAT!"))
+    Solution(BooleanLiteral(false), Set(), Error(tpe, "Path condition is UNSAT!"))
   }
 }