fix lint errors

archivebox/main.py

@@ -94,7 +94,6 @@ from .config import (
     EXTERNAL_LOCATIONS,
     DATA_LOCATIONS,
     DEPENDENCIES,
-    USE_CHROME,
     CHROME_BINARY,
     CHROME_VERSION,
     YOUTUBEDL_BINARY,
@@ -102,8 +101,6 @@ from .config import (
     SINGLEFILE_VERSION,
     READABILITY_VERSION,
     MERCURY_VERSION,
-    USE_YOUTUBEDL,
-    USE_NODE,
     NODE_VERSION,
     load_all_config,
     CONFIG,