Fix flake8 complaint.

...

Author: StyXman

rest_framework_docs/api_docs.py

@@ -25,7 +25,7 @@ def get_all_view_names(self, urlpatterns, parent_regex=None):
         for pattern in urlpatterns:
             if isinstance(pattern, RegexURLResolver):
                 regex = '' if pattern._regex == "^" else pattern._regex
-                self.get_all_view_names(urlpatterns=pattern.url_patterns, parent_regex=parent_regex+regex)
+                self.get_all_view_names(urlpatterns=pattern.url_patterns, parent_regex=parent_regex + regex)
             elif isinstance(pattern, RegexURLPattern) and self._is_drf_view(pattern) and not self._is_format_endpoint(pattern):
                 api_endpoint = ApiEndpoint(pattern, parent_regex, self.drf_router)
                 self.endpoints.append(api_endpoint)