Fix no-std compilation

r1cs-std/src/test_constraint_system.rs

@@ -132,10 +132,10 @@ impl TestConstraintSystem {
 
 fn compute_path(ns: &[String], this: String) -> String {
     if this.chars().any(|a| a == '/') {
-        panic!(format!(
-            "'/' is not allowed in namespace names. Error in namespace name: {:?}",
+        panic!(
+            "'/' is not allowed in namespaces. Error in namespace '{}'",
             this
-        ));
+        );
     }
 
     let mut name = String::new();