requests_fetcher: Add missing 'tuf' import

Code uses tuf.__version__ for user-agent.

Signed-off-by: Jussi Kukkonen <[email protected]>

Author: Jussi Kukkonen

tuf/requests_fetcher.py

@@ -12,6 +12,7 @@
 import time
 from urllib3.exceptions import ReadTimeoutError
 
+import tuf
 from tuf import exceptions
 from tuf import settings