Forward port of r64958.
Added '#' formatting to integers.  This adds the 0b, 0o, or 0x prefix for bin, oct, hex.  There's still one failing case, and I need to finish the docs.  I hope to finish those today.
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index fb904bf..e6b3cb0 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -700,6 +700,10 @@
         self.assertRaises(ValueError, format, "", "-")
         self.assertRaises(ValueError, "{0:=s}".format, '')
 
+        # Alternate formatting is not supported
+        self.assertRaises(ValueError, format, '', '#')
+        self.assertRaises(ValueError, format, '', '#20')
+
     def test_formatting(self):
         string_tests.MixinStrUnicodeUserStringTest.test_formatting(self)
         # Testing Unicode formatting strings...