refact(TCs) skip xs xfail for py3.6 string asserts

Author: ankostis

test/test_plot.py

@@ -547,7 +547,7 @@ def dot_str_pipeline():
     )
 
 
-@pytest.mark.xfail(
+@pytest.mark.skipif(
     sys.version_info < (3, 7), reason="PY3.6- have different docstrings for builtins."
 )
 def test_node_dot_str0(dot_str_pipeline):
@@ -605,7 +605,7 @@ def test_node_dot_str0(dot_str_pipeline):
     assert _striplines(dot_str) == _striplines(exp)
 
 
-@pytest.mark.xfail(
+@pytest.mark.skipif(
     sys.version_info < (3, 7), reason="PY3.6 - has different docstrings for builtins."
 )
 def test_node_dot_str1(dot_str_pipeline, monkeypatch):

test/test_sideffects.py

@@ -333,7 +333,7 @@ def finalize_prices(order: DataFrame) -> Tuple[DataFrame, float]:
     return compose("process order", *ops, parallel=exemethod)
 
 
-@pytest.mark.xfail(
+@pytest.mark.skipif(
     sys.version_info < (3, 7),
     reason="Pickling function typing of return annotations fails.",
 )
@@ -380,7 +380,7 @@ def test_sideffecteds_ok(calc_prices_pipeline):
     assert re.search(r'(?s)>vat owed<.+tooltip=".*\(evicted\)"', dot)
 
 
-@pytest.mark.xfail(
+@pytest.mark.skipif(
     sys.version_info < (3, 7),
     reason="Pickling function typing of return annotations fails.",
 )