Fix async_helpers tests

Many of the tests were simply executing code and ignoring errors
(including several which had errors in them). This commit makes it so
that errors are actually raised, and fixes the errors in code that had
them.

IPython/core/tests/test_async_helpers.py

@@ -10,8 +10,7 b' from textwrap import dedent, indent'
 from unittest import TestCase
 
 ip = get_ipython()
-iprc = lambda x: ip.run_cell(dedent(x))
-iprc_err = lambda x: iprc(x).raise_error()
+iprc = lambda x: ip.run_cell(dedent(x)).raise_error()
 
 if sys.version_info > (3, 5):
     from IPython.core.async_helpers import _should_be_async
@@ -142,14 +141,14 b' if sys.version_info > (3, 5):'
             for test_name, test_case in tl_err_test_cases:
                 # This example should work if 'pass' is used as the value
                 with self.subTest((test_name, 'pass')):
-                    iprc_err(test_case.format(val='pass'))
+                    iprc(test_case.format(val='pass'))
 
                 # It should fail with all the values
                 for val in vals:
                     with self.subTest((test_name, val)):
                         msg = "Syntax error not raised for %s, %s" % (test_name, val)
                         with self.assertRaises(SyntaxError, msg=msg):
-                            iprc_err(test_case.format(val=val))
+                            iprc(test_case.format(val=val))
 
         def test_in_func_no_error(self):
             # Test that the implementation of top-level return/yield
@@ -197,7 +196,7 b' if sys.version_info > (3, 5):'
 
                     for val in vals:
                         with self.subTest((test_name, context_name, val)):
-                            iprc_err(nested_case.format(val=val))
+                            iprc(nested_case.format(val=val))
 
                 # These tests should still raise a SyntaxError
                 for test_name, test_case in failure_tests:
@@ -206,32 +205,30 b' if sys.version_info > (3, 5):'
                     for val in vals:
                         with self.subTest((test_name, context_name, val)):
                             with self.assertRaises(SyntaxError):
-                                iprc_err(nested_case.format(val=val))
+                                iprc(nested_case.format(val=val))
 
 
         def test_execute(self):
-            iprc(
-                """
+            iprc("""
             import asyncio
             await asyncio.sleep(0.001)
             """
             )
 
         def test_autoawait(self):
-            ip.run_cell("%autoawait False")
-            ip.run_cell("%autoawait True")
-            iprc(
-                """
-                from asyncio import sleep
-                await.sleep(0.1)
+            iprc("%autoawait False")
+            iprc("%autoawait True")
+            iprc("""
+            from asyncio import sleep
+            await sleep(0.1)
             """
             )
 
         def test_autoawait_curio(self):
-            ip.run_cell("%autoawait curio")
+            iprc("%autoawait curio")
 
         def test_autoawait_trio(self):
-            ip.run_cell("%autoawait trio")
+            iprc("%autoawait trio")
 
         def tearDown(self):
             ip.loop_runner = "asyncio"