Every time that there's freqtrade "ticks", pairs in the blacklist are
checked and a warning message is displayed.
So, the logs are continuously flooded with the same warnings.
For example:
2021-07-26 06:24:45 freqtrade.plugins.pairlistmanager: WARNING -
Pair XTZUP/USDT in your blacklist. Removing it from whitelist...
2021-07-26 06:24:45 freqtrade.plugins.pairlistmanager: WARNING -
Pair SUSHIUP/USDT in your blacklist. Removing it from whitelist...
2021-07-26 06:24:45 freqtrade.plugins.pairlistmanager: WARNING -
Pair XTZDOWN/USDT in your blacklist. Removing it from whitelist...
2021-07-26 06:24:50 freqtrade.plugins.pairlistmanager: WARNING -
Pair XTZUP/USDT in your blacklist. Removing it from whitelist...
2021-07-26 06:24:50 freqtrade.plugins.pairlistmanager: WARNING -
Pair SUSHIUP/USDT in your blacklist. Removing it from whitelist...
2021-07-26 06:24:50 freqtrade.plugins.pairlistmanager: WARNING -
Pair XTZDOWN/USDT in your blacklist. Removing it from whitelist...
This patch shows the warning only the first time, by keeping track
of which pairs in the blacklist were already logged.