Kucoin trade subscription fails since ~10 feb.

[kozy]

Describe the bug
In cryptofeed v2.4.1, the KuCoin exchange adapter constructs WebSocket subscription topics with a space after the colon delimiter:

/market/match: BTC-USDT

KuCoin’s WebSocket API requires the topic to be formatted without whitespace:

/market/match:BTC-USDT

As a result, KuCoin returns:

{'id': '1', 'type': 'error', 'code': 400, 'data': 'topic /market/match: BTC-USDT is invalid'}

This affects both single-symbol and multi-symbol subscriptions and causes all trade subscriptions to fail.

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To Reproduce

Small reproducible example:

from cryptofeed import FeedHandler
from cryptofeed.defines import TRADES
from cryptofeed.exchanges import KuCoin

async def trade(t, receipt_timestamp):
    print(t)

fh = FeedHandler()
fh.add_feed(
    KuCoin(
        symbols=["BTC-USDT"],
        channels=[TRADES],
        callbacks={TRADES: trade},
    )
)
fh.run()

Observed error:

WARNING: KUCOIN: error from exchange {
    'id': '1',
    'type': 'error',
    'code': 400,
    'data': 'topic /market/match: BTC-USDT is invalid'
}

Inspection of cryptofeed/exchanges/kucoin.py (v2.4.1) shows:

'topic': f"{chan}: {','.join(...)}"

The space after : results in an invalid topic string per KuCoin’s API grammar.

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Expected behavior
The KuCoin adapter should emit:

/market/match:BTC-USDT

without whitespace after the colon, matching KuCoin’s documented topic format.

Subscriptions should succeed and trades should stream normally.

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Screenshots
N/A

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Operating System:
Linux (reproduced on x86_64)

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Cryptofeed Version
2.4.1 (installed from PyPI via pip)