Prevent keyring from ever reading from stdin

It shouldn't need to ever so no reason to allow it and have
to jiggle around the `--no-input` option in `pip`.

Author: judahrand

src/pip/_internal/network/auth.py

@@ -47,7 +47,10 @@ def __init__(self, keyring: str) -> None:
     def get_password(self, service_name: str, username: str) -> Optional[str]:
         cmd = [self.keyring, "get", service_name, username]
         res = subprocess.run(
-            cmd, capture_output=True, env=dict(PYTHONIOENCODING="utf-8")
+            cmd,
+            stdin=subprocess.DEVNULL,
+            capture_output=True,
+            env=dict(PYTHONIOENCODING="utf-8"),
         )
         if res.returncode:
             return None