test: Mark MANPATH without leading/trailing colons test an xfail on C…

…I CentOS 6

test/t/test_man.py

@@ -1,3 +1,5 @@
+import os
+
 import pytest
 
 
@@ -20,6 +22,13 @@ def test_2(self, completion):
     def test_3(self, completion):
         assert completion.list == ["man/quux.8"]
 
+    @pytest.mark.xfail(os.environ.get("CI") and
+                       os.environ.get("DIST") == "centos6",
+                       reason="TODO: Fails in CentOS for some reason, unknown "
+                       "how to trigger same behavior as tests show (is "
+                       "different and correct when tried manually, but here "
+                       "at least in CI completes things it should not with "
+                       "this MANPATH setting)")
     @pytest.mark.complete("man %s" % assumed_present, cwd="shared/empty_dir",
                           env=dict(MANPATH=manpath))
     def test_4(self, completion):