fix Python 3.8 and 3.9 compatibility, second attempt

Try, try, try again until it works;
Merrily, merrily, merrily, until it works.

unpythonic/syntax/tests/test_letdo.py

@@ -33,7 +33,7 @@ def runtests():
         #    Assignment expressions can now be used unparenthesized within set literals and set comprehensions, as well as in sequence indexes (but not slices).
         d1 = do[local[(x := 17)],
                 print(x),
-                x := 23,
+                (x := 23),
                 x]
         test[d1 == 23]
 

unpythonic/syntax/tests/test_letdoutil.py

@@ -346,7 +346,7 @@ def testletdestructuring(testdata):
         testletdestructuring(testdata)
 
         # haskelly let-where
-        testdata = q[let[y * x, where[x := 21, y := 2]]]  # noqa: F821
+        testdata = q[let[y * x, where[(x := 21), (y := 2)]]]  # noqa: F821
         testletdestructuring(testdata)
         testdata = q[let[y * x, where[x << 21, y << 2]]]  # noqa: F821
         testletdestructuring(testdata)