try this

CamDavidsonPilon · CamDavidsonPilon · commit 1b3856955938 · 2019-11-08T09:20:19.000-05:00
diff --git a/lifelines/tests/test_requirements.py b/lifelines/tests/test_requirements.py
@@ -6,7 +6,7 @@
 
 
 BASE_PATH = Path(__file__).parent.parent.parent
-REQUIREMENTS_PATH = BASE_PATH.joinpath("reqs/base-requirements.txt").absolute()
+REQUIREMENTS_PATH = str(BASE_PATH.joinpath("reqs/base-requirements.txt").absolute())
 
 
 class TestRequirements:
