Use str from builtins
@@ -17,6 +17,7 @@ from six import PY2, StringIO
from readthedocs.core.validators import validate_submodule_url
from readthedocs.projects.exceptions import RepositoryError
from readthedocs.vcs_support.base import BaseVCS, VCSVersion
+from builtins import str
log = logging.getLogger(__name__)
