re #329 add test for skipif failure when you pass boolean without the reason. add emphasize to the docs.

--HG--
branch : 329-skipif-requires-expression-as-a-string

doc/en/skipping.txt

@@ -44,6 +44,7 @@ During test function setup the condition ("sys.version_info >= (3,3)") is
 checked.  If it evaluates to True, the test function will be skipped
 with the specified reason.  Note that pytest enforces specifying a reason
 in order to report meaningful "skip reasons" (e.g. when using ``-rs``).
+If the condition is a string, it will be evaluated as python expression.
 
 You can share skipif markers between modules.  Consider this test module::
 

testing/test_skipping.py

@@ -100,6 +100,18 @@ class TestEvaluator:
         expl = ev.getexplanation()
         assert expl == "condition: not hasattr(os, 'murks')"
 
+    def test_marked_skip_with_not_string(self, testdir):
+        item = testdir.getitem("""
+            import pytest
+            @pytest.mark.skipif(False)
+            def test_func():
+                pass
+        """)
+        ev = MarkEvaluator(item, 'skipif')
+        with pytest.raises(pytest.fail.Exception) as exc:
+            assert ev.istrue()
+        assert """Failed: you need to specify reason=STRING when using booleans as conditions.""" in exc.value.msg
+
     def test_skipif_class(self, testdir):
         item, = testdir.getitems("""
             import pytest