tests/basics: Add test cases for context manager raising in enter/exit.

tests/basics/with_raise.py

+# test with when context manager raises in __enter__/__exit__
+
+class CtxMgr:
+    def __init__(self, id):
+        self.id = id
+
+    def __enter__(self):
+        print("__enter__", self.id)
+        if 10 <= self.id < 20:
+            raise Exception('enter', self.id)
+        return self
+
+    def __exit__(self, a, b, c):
+        print("__exit__", self.id, repr(a), repr(b))
+        if 15 <= self.id < 25:
+            raise Exception('exit', self.id)
+
+# no raising
+try:
+    with CtxMgr(1):
+        pass
+except Exception as e:
+    print(e)
+
+# raise in enter
+try:
+    with CtxMgr(10):
+        pass
+except Exception as e:
+    print(e)
+
+# raise in enter and exit
+try:
+    with CtxMgr(15):
+        pass
+except Exception as e:
+    print(e)
+
+# raise in exit
+try:
+    with CtxMgr(20):
+        pass
+except Exception as e:
+    print(e)