diff -r dc0811953034 Lib/doctest.py
--- a/Lib/doctest.py	Fri Mar 25 12:50:54 2016 +0100
+++ b/Lib/doctest.py	Fri Mar 25 12:57:11 2016 +0100
@@ -397,6 +397,10 @@ def _module_relative_path(module, path):
             basedir = os.path.split(sys.argv[0])[0]
         else:
             basedir = os.curdir
+    elif hasattr(module, '__path__') and len(module.__path__) == 1:
+        # Heuristic for package: if the package is only made of one directory,
+        # use this directory
+        basedir = list(module.__path__)[0]
     else:
         # A module w/o __file__ (this includes builtins)
         raise ValueError("Can't resolve paths relative to the module "