avoid wasting time on parsing pyregr test files for Cython tags

runtests.py

@@ -448,6 +448,9 @@ class TestBuilder(object):
                 continue
             if filename.startswith('.'):
                 continue # certain emacs backup files
+            if context == 'pyregr':
+                tags = defaultdict(list)
+            else:
                 tags = parse_tags(filepath)
             fqmodule = "%s.%s" % (context, module)
             if not [ 1 for match in self.selectors