PEP 572: use double backticks for the ``with`` keyword. (#716)

pep-0572.rst

@@ -711,7 +711,7 @@ above, proposals have been made for comprehension-specific solutions.
 
        stuff = [(y, x/y) with y = f(x) for x in range(5)]
 
-   As above, but reusing the `with` keyword. Doesn't read too badly, and needs
+   As above, but reusing the ``with`` keyword. Doesn't read too badly, and needs
    no additional language keyword. Is restricted to comprehensions, though,
    and cannot as easily be transformed into "longhand" for-loop syntax. Has
    the C problem that an equals sign in an expression can now create a name