doctest assumed that a package's __loader__.get_data() method used universal
newlines; it doesn't.  To rectify this the string returned replaces all
instances of os.linesep with '\n' to fake universal newline support.

Backport candidate.
diff --git a/Misc/NEWS b/Misc/NEWS
index c474c50..ddba8b8 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -284,6 +284,9 @@
 Library
 -------
 
+- doctest made a bad assumption that a package's __loader__.get_data()
+  method used universal newlines.
+
 - Issue #1705170: contextlib.contextmanager was still swallowing
   StopIteration in some cases. This should no longer happen.