Tests: cli: Detect and handle the -d '' case

yamllint/cli.py

@@ -88,7 +88,7 @@ def run(argv=None):
 
     try:
         if args.config_data is not None:
-            if ':' not in args.config_data:
+            if args.config_data != '' and ':' not in args.config_data:
                 args.config_data = 'extends: ' + args.config_data
             conf = YamlLintConfig(content=args.config_data)
         elif args.config_file is not None:

yamllint/config.py

@@ -59,6 +59,9 @@ class YamlLintConfig(object):
         except Exception as e:
             raise YamlLintConfigError('invalid config: %s' % e)
 
+        if type(conf) != dict:
+            raise YamlLintConfigError('invalid config: not a dict')
+
         self.rules = conf.get('rules', {})
 
         # Does this conf override another conf that we need to load?