Fix some test on python 3.9 (nightly).

Mostly

1) Pgen parser does not raise MemorryError anymore.
2) Function signature now understand "Optinal" correctly

IPython/core/tests/test_async_helpers.py

@@ -8,7 +8,7 b' import nose.tools as nt'
 from textwrap import dedent, indent
 from unittest import TestCase
 from IPython.testing.decorators import skip_without
-
+import sys
 
 iprc = lambda x: ip.run_cell(dedent(x)).raise_error()
 iprc_nr = lambda x: ip.run_cell(dedent(x))
@@ -275,10 +275,13 b' class AsyncTest(TestCase):'
         await sleep(0.1)
         """
         )
-
-    def test_memory_error(self):
-        with self.assertRaises(MemoryError):
-            iprc("(" * 200 + ")" * 200)
+    
+    if sys.version_info < (3,9):
+        # new pgen parser in 3.9 does not raise MemoryError on too many nested
+        # parens anymore
+        def test_memory_error(self):
+            with self.assertRaises(MemoryError):
+                iprc("(" * 200 + ")" * 200)
 
     @skip_without('curio')
     def test_autoawait_curio(self):

IPython/core/tests/test_oinspect.py

@@ -421,6 +421,14 b' def test_render_signature_long():'
         long_function.__name__,
     )
     nt.assert_in(sig, [
+        # Python >=3.9
+        '''\
+long_function(
+    a_really_long_parameter: int,
+    and_another_long_one: bool = False,
+    let_us_make_sure_this_is_looong: Optional[str] = None,
+) -> bool\
+''',
         # Python >=3.7
         '''\
 long_function(

IPython/core/tests/test_ultratb.py

@@ -247,12 +247,16 b' bar()'
             with tt.AssertPrints('QWERTY'):
                 ip.showsyntaxerror()
 
-
-class MemoryErrorTest(unittest.TestCase):
-    def test_memoryerror(self):
-        memoryerror_code = "(" * 200 + ")" * 200
-        with tt.AssertPrints("MemoryError"):
-            ip.run_cell(memoryerror_code)
+import sys
+if sys.version_info < (3,9):
+    """
+    New 3.9 Pgen Parser does not raise Memory error, except on failed malloc.
+    """
+    class MemoryErrorTest(unittest.TestCase):
+        def test_memoryerror(self):
+            memoryerror_code = "(" * 200 + ")" * 200
+            with tt.AssertPrints("MemoryError"):
+                ip.run_cell(memoryerror_code)
 
 
 class Python3ChainedExceptionsTest(unittest.TestCase):