Only overwrite spec file if we succeed in generating spec

Author: vidartf

packages/schema/generate-spec.py

@@ -237,14 +237,15 @@ def create_markdown(spec):
     args = parser.parse_args()
     format = args.format
 
+    widgets_to_document = sorted(widgets.Widget._widget_types.items())
+    spec = create_spec(widgets_to_document)
+
     if args.output:
         args.output.parent.mkdir(exist_ok=True)
         output = open(args.output, mode='w', encoding='utf8')
     else:
         output = sys.stdout
 
-    widgets_to_document = sorted(widgets.Widget._widget_types.items())
-    spec = create_spec(widgets_to_document)
     try:
         if format == 'json':
             try: