diff -r e5478b6b93b5 Lib/doctest.py
--- a/Lib/doctest.py	Sat Jun 23 10:06:56 2012 +0200
+++ b/Lib/doctest.py	Mon Jun 25 15:18:28 2012 +0200
@@ -2767,17 +2767,20 @@
         print("usage: {0} [-v] file ...".format(name))
         return 2
     for filename in testfiles:
-        if filename.endswith(".py"):
-            # It is a module -- insert its dir into sys.path and try to
-            # import it. If it is part of a package, that possibly
-            # won't work because of package imports.
-            dirname, filename = os.path.split(filename)
-            sys.path.insert(0, dirname)
-            m = __import__(filename[:-3])
-            del sys.path[0]
-            failures, _ = testmod(m)
-        else:
-            failures, _ = testfile(filename, module_relative=False)
+        try:
+            if filename.endswith(".py"):
+                # It is a module -- insert its dir into sys.path and try to
+                # import it. If it is part of a package, that possibly
+                # won't work because of package imports.
+                dirname, filename = os.path.split(filename)
+                sys.path.insert(0, dirname)
+                m = __import__(filename[:-3])
+                del sys.path[0]
+                failures, _ = testmod(m)
+            else:
+                failures, _ = testfile(filename, module_relative=False)
+        except IOError as e:
+            sys.exit("Cannot read '{0}': {1}".format(filename, e))
         if failures:
             return 1
     return 0