test: use conftest.py to skip PEP563 tests for python 3.6

Author: ydylla

conftest.py

@@ -0,0 +1,8 @@
+# see https://docs.pytest.org/en/latest/example/pythoncollection.html#customizing-test-collection
+import sys
+
+collect_ignore = ["setup.py"]
+
+if sys.version_info[:2] == (3, 6):
+    # skip these tests for python 3.6 because it does not support PEP 563
+    collect_ignore.append("tests/test_lazy_type_evaluation.py")