Added call to check_schema before checking instance

Author: William Speirs

jsonschema/cli.py

@@ -65,6 +65,10 @@ def run(arguments, stdout=sys.stdout, stderr=sys.stderr):
     error_format = arguments["error_format"]
     validator = arguments["validator"](schema=arguments["schema"])
     errored = False
+
+    # add a check to the schema file first
+    validator.check_schema(arguments["schema"])
+
     for instance in arguments["instances"] or ():
         for error in validator.iter_errors(instance):
             stderr.write(error_format.format(error=error))