Fix a legacy raise statement in pickle's docs.
diff --git a/Doc/library/pickle.rst b/Doc/library/pickle.rst
index dace18a..9bbb1d3 100644
--- a/Doc/library/pickle.rst
+++ b/Doc/library/pickle.rst
@@ -592,7 +592,7 @@
            value = int(persid.split()[2])
            return FancyInteger(value)
        else:
-           raise pickle.UnpicklingError, 'Invalid persistent id'
+           raise pickle.UnpicklingError('Invalid persistent id')
 
    up.persistent_load = persistent_load