Fix test

Call mkdocs with relative path
we are already setting the cwd to the full checkout path

Author: stsewd

readthedocs/doc_builder/backends/mkdocs.py

@@ -248,7 +248,7 @@ def build(self):
             '--site-dir',
             self.build_dir,
             '--config-file',
-            self.yaml_file,
+            os.path.relpath(self.yaml_file, self.root_path),
         ]
         if self.config.mkdocs.fail_on_warning:
             build_command.append('--strict')