Here is a patch that hopefully does what was intended. All the tests passed locally, hopefully the tests we're adapted correctly to the new location of the files. My first patch :)

I added a new "data" file 'doctest_DocFileSuite_test.txt' to Lib/test to keep the test that tests that doctest.DocFileSuite loads files from calling module path. All the old files I moved to Lib/test/doctest and adapted tests to use them from there.