Force string in get_user_agent for test network session

Author: notatallshaw

tests/unit/test_network_session.py

@@ -28,7 +28,7 @@ def get_user_agent() -> str:
     # These tests are testing the computation of the user agent, so we want to
     # avoid reusing cached values.
     user_agent.cache_clear()
-    return PipSession().headers["User-Agent"]
+    return str(PipSession().headers["User-Agent"])
 
 
 def test_user_agent() -> None: