Do not implement pytest_logwarning in pytest versions where it is deprecated

Fix #406

Author: nicoddemus

changelog/406.bugfix.rst

@@ -0,0 +1 @@
+Do not implement deprecated ``pytest_logwarning`` hook in pytest versions where it is deprecated.

xdist/remote.py

@@ -115,8 +115,10 @@ def pytest_collectreport(self, report):
             data = serialize_report(report)
             self.sendevent("collectreport", data=data)
 
-    # the pytest_logwarning hook was removed in pytest 4.1
-    if hasattr(_pytest.hookspec, "pytest_logwarning"):
+    # the pytest_logwarning hook was deprecated since pytest 4.0
+    if hasattr(
+        _pytest.hookspec, "pytest_logwarning"
+    ) and not _pytest.hookspec.pytest_logwarning.pytest_spec.get("warn_on_impl"):
 
         def pytest_logwarning(self, message, code, nodeid, fslocation):
             self.sendevent(