expression tests: adjust starred expression for Python 3.9 (#1441) (#1477)

As discussed in #1441, Python 3.9's new parser will not parse
`(*starred)` even using `compile()` with the `PyCF_ONLY_AST`
flag (as `ast.parse()` does), it raises a `SyntaxError`. This
breaks the four tests that use this file with Python 3.9.
Upstream does not consider this to be a bug - see
https://bugs.python.org/issue40848#msg370643 - so we must
adjust the expression. As suggested by @JelleZijlstra, this just
adds a comma, which makes the new parser happy with it (the old
parser is fine with this form also).

Signed-off-by: Adam Williamson <awilliam@redhat.com>

tests/data/expression.diff

@@ -179,7 +179,7 @@
 -((i ** 2) for i, _ in ((1, 'a'), (2, 'b'), (3, 'c')))
 +((i ** 2) for i, _ in ((1, "a"), (2, "b"), (3, "c")))
  (((i ** 2) + j) for i in (1, 2, 3) for j in (1, 2, 3))
- (*starred)
+ (*starred,)
 -{"id": "1","type": "type","started_at": now(),"ended_at": now() + timedelta(days=10),"priority": 1,"import_session_id": 1,**kwargs}
 +{
 +    "id": "1",

tests/data/expression.py

@@ -146,7 +146,7 @@
 ((i ** 2) for i in (1, 2, 3))
 ((i ** 2) for i, _ in ((1, 'a'), (2, 'b'), (3, 'c')))
 (((i ** 2) + j) for i in (1, 2, 3) for j in (1, 2, 3))
-(*starred)
+(*starred,)
 {"id": "1","type": "type","started_at": now(),"ended_at": now() + timedelta(days=10),"priority": 1,"import_session_id": 1,**kwargs}
 a = (1,)
 b = 1,
@@ -431,7 +431,7 @@ async def f():
 ((i ** 2) for i in (1, 2, 3))
 ((i ** 2) for i, _ in ((1, "a"), (2, "b"), (3, "c")))
 (((i ** 2) + j) for i in (1, 2, 3) for j in (1, 2, 3))
-(*starred)
+(*starred,)
 {
     "id": "1",
     "type": "type",