fix: improves parsing error and includes only original error message (validateBody)

Author: artem-zakharchenko

lib/units/validateBody.js

@@ -161,10 +161,10 @@ Failed to parse a given JSON Schema:
 
 ${schema}
 
-Please check if that is a valid JSON and a valid JSON Schema.
+Please check that the given JSON Schema is a valid JSON.
 
 Original parsing error:
-${error.stack}\
+${error.message}\
     `);
   }
 };
@@ -193,7 +193,9 @@ function validateBody(expected, real) {
   );
 
   // Attempt to parse a given JSON Schema
-  // in case it's a raw string.
+  // to verify that it's a valid JSON.
+  // TODO Move this into an input validation layer
+  // once such is introduced.
   if (typeof expected.bodySchema === 'string') {
     validateJsonSchema(expected.bodySchema);
   }