Add the last line to the info message

Author: pradyunsg

src/pip/_internal/resolution/resolvelib/reporter.py

@@ -35,6 +35,8 @@ def __init__(self):
                 "This is taking longer than usual. You might need to provide the "
                 "dependency resolver with stricter constraints to reduce runtime."
                 "If you want to abort this run, you can press Ctrl + C to do so."
+                "To improve how pip performs, tell us that this happened here: "
+                "https://pip.pypa.io/surveys/backtracking"
             )
         }