TMSS-917: raise more specific json decode error

SAS/TMSS/client/lib/populate.py

@@ -45,11 +45,12 @@ def populate_schemas(schema_dir: str=None, templates_filename: str=None):
             # load all templates and schemas and prepare them for upload.
             # determine the dependencies, and upload the depenends first, and the rest in parallel later.
             for template in templates:
+                with open(os.path.join(schema_dir, template['file_name'])) as schema_file:
+                    content = schema_file.read()
                 try:
-                    with open(os.path.join(schema_dir, template['file_name'])) as schema_file:
-                        json_schema = json.loads(schema_file.read())
+                    json_schema = json.loads(content)
                 except Exception as e:
-                    raise Exception("Could not decode JSON schema %s" % template['file_name']) from e
+                    raise Exception("Could not decode JSON schema file: '%s'\n%s" % (template['file_name'], content)) from e
 
                 # add template name/description/version from schema if not already in template
                 template['name'] = template.get('name', json_schema.get('title', '<no name>'))