Avro Schema Evolution

import copy, io, json
from fastavro import parse_schema as parse, schemaless_reader, schemaless_writer
from orders_io import orders
v1 = json.load(open("order.avsc"))
buf = io.BytesIO()
schemaless_writer(buf, parse(v1), next(orders()))             # data written with version 1
v2 = copy.deepcopy(v1)                                         # the reader's evolved schema
f = {x["name"]: x for x in v2["fields"]}
f["customer_id"]["type"] = "long"                              # promote int -> long
f["channel"].update(name="sales_channel", aliases=["channel"])  # rename via an alias
v2["fields"].remove(f["currency"])                             # dropped: value skipped
v2["fields"].append({"name": "gift_wrap", "type": "boolean", "default": False})
v3 = copy.deepcopy(v2)
v3["fields"].append({"name": "gift_note", "type": "string"})   # added without a default
for name, reader in (("v2", v2), ("v3", v3)):
    buf.seek(0)
    try:
        rec = schemaless_reader(buf, parse(v1), parse(reader))
        print(name, {k: rec[k] for k in ("customer_id", "sales_channel", "gift_wrap")})
    except Exception as e:
        print(name, f"{type(e).__name__}: {e}")

v2 {'customer_id': 2518, 'sales_channel': 'ios', 'gift_wrap': False}
v3 SchemaResolutionError: No default value for field gift_note in com.example.booknest.Order