#15916: if there are no docstrings, make empty suite, not an error.
This makes doctest work like unittest: if the test case is empty, that
just means there are zero tests run, it's not an error. The existing
behavior was broken, since it only gave an error if there were *no*
docstrings, and zero tests run if there were docstrings but none of them
contained tests. So this makes it self-consistent as well.
Patch by Glenn Jones.
diff --git a/Doc/whatsnew/3.5.rst b/Doc/whatsnew/3.5.rst
index 7050e0a..b9ad684 100644
--- a/Doc/whatsnew/3.5.rst
+++ b/Doc/whatsnew/3.5.rst
@@ -154,6 +154,10 @@
applications where startup time is paramount (contributed by Brett Cannon in
:issue:`17621`).
+* :func:`doctest.DocTestSuite` returns an empty :class:`unittest.TestSuite` if
+ *module* contains no docstrings instead of raising :exc:`ValueError`
+ (contributed by Glenn Jones in :issue:`15916`).
+
Optimizations
=============