Fix null rule for syntax error

Signed-off-by: Mathieu Rul <mathroule@gmail.com>

tests/common.py

@@ -40,10 +40,7 @@ class RuleTestCase(unittest.TestCase):
         for key in kwargs:
             assert key.startswith('problem')
             if len(kwargs[key]) > 2:
-                if kwargs[key][2] == 'syntax':
-                    rule_id = None
-                else:
-                    rule_id = kwargs[key][2]
+                rule_id = kwargs[key][2]
             else:
                 rule_id = self.rule_id
             expected_problems.append(linter.LintProblem(

tests/test_syntax_errors.py

@@ -17,7 +17,7 @@ from tests.common import RuleTestCase
 
 
 class YamlLintTestCase(RuleTestCase):
-    rule_id = None  # syntax error
+    rule_id = 'syntax'  # syntax error
 
     def test_syntax_errors(self):
         self.check('---\n'

yamllint/linter.py

@@ -180,7 +180,8 @@ def get_syntax_error(buffer):
     except yaml.error.MarkedYAMLError as e:
         problem = LintProblem(e.problem_mark.line + 1,
                               e.problem_mark.column + 1,
-                              'syntax error: ' + e.problem + ' (syntax)')
+                              'syntax error: ' + e.problem,
+                              'syntax')
         problem.level = 'error'
         return problem