tests(pytest): doctest -> xdoctest

See also: https://github.com/Erotemic/xdoctest/tree/v1.0.0#using-the-native-interface

Author: tony

setup.cfg

@@ -17,5 +17,5 @@ sections = FUTURE,STDLIB,PYTEST,THIRDPARTY,FIRSTPARTY,LOCALFOLDER
 line_length = 88
 
 [tool:pytest]
-addopts = --tb=short --no-header --showlocals --doctest-modules
+addopts = --tb=short --no-header --showlocals --xdoctest
 doctest_optionflags = ELLIPSIS NORMALIZE_WHITESPACE