Merge pull request #4944 from henrykironde/k-EXPRESSION

Add example for k flag

src/_pytest/mark/__init__.py

@@ -52,6 +52,7 @@ def pytest_addoption(parser):
         "other' matches all test functions and classes whose name "
         "contains 'test_method' or 'test_other', while -k 'not test_method' "
         "matches those that don't contain 'test_method' in their names. "
+        "-k 'not test_method and not test_other' will eliminate the matches. "
         "Additionally keywords are matched to classes and functions "
         "containing extra names in their 'extra_keyword_matches' set, "
         "as well as functions which have names assigned directly to them.",