Merge 3.2: Issue #13703 plus some related test suite fixes.
diff --git a/Objects/object.c b/Objects/object.c
index 8134825..bb18d47 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -759,10 +759,19 @@
     Py_uhash_t x;
     Py_ssize_t i;
 
-    x = (Py_uhash_t) *p << 7;
+    /*
+      We make the hash of the empty string be 0, rather than using
+      (prefix ^ suffix), since this slightly obfuscates the hash secret
+    */
+    if (len == 0) {
+        return 0;
+    }
+    x = (Py_uhash_t) _Py_HashSecret.prefix;
+    x ^= (Py_uhash_t) *p << 7;
     for (i = 0; i < len; i++)
         x = (_PyHASH_MULTIPLIER * x) ^ (Py_uhash_t) *p++;
     x ^= (Py_uhash_t) len;
+    x ^= (Py_uhash_t) _Py_HashSecret.suffix;
     if (x == -1)
         x = -2;
     return x;
@@ -776,6 +785,8 @@
     return -1;
 }
 
+_Py_HashSecret_t _Py_HashSecret;
+
 Py_hash_t
 PyObject_Hash(PyObject *v)
 {