The problem is that the certificate file can be rewritten by another
dictionary setup, look at [1]:

First of all server contains fatal errors in logs, and it should be a
starting point:

    Traceback (most recent call last):
      File "/http_server.py", line 116, in <module>
        start_server(
      File "/http_server.py", line 90, in start_server
        httpd.socket = ssl.wrap_socket(
      File "/usr/lib/python3.10/ssl.py", line 1468, in wrap_socket
        context.load_cert_chain(certfile, keyfile)
    ssl.SSLError: [SSL] PEM lib (_ssl.c:3900)

Next we can look at pytest logs:

    2025-08-01 13:26:29.588000 [ 652 ] DEBUG : Command:[docker exec roottestdictionariesalllayoutsseparatesourceshttps-gw2-clickhouse_hs-1 bash -c mkdir -p $(dirname /fake_cert.pem) && echo ... | base64 --decode > /fake_cert.pem] (cluster.py:119, run_and_check)
    2025-08-01 13:26:29.857000 [ 652 ] DEBUG : Command:[docker exec roottestdictionariesalllayoutsseparatesourceshttps-gw2-clickhouse_hs-1 bash -c mkdir -p $(dirname /fake_cert.pem) && echo ... | base64 --decode > /fake_cert.pem] (cluster.py:119, run_and_check)
    2025-08-01 13:26:29.909000 [ 652 ] DEBUG : run container_id:roottestdictionariesalllayoutsseparatesourceshttps-gw2-clickhouse_hs-1 detach:True nothrow:False cmd: ['bash', '-c', 'python3 /http_server.py --data-path=/table_SourceHTTPS_hashed_.tsv --schema=https --host=clickhouse_hs --port=5556 --cert-path=/fake_cert.pem >> /var/log/clickhouse-server/http_server.py.log 2>&1'] (cluster.py:2170, exec_in_container)

It does multiple copying of fake_cert.pem, but, it is not synced with
reading of this file in http-server.py

So, let's make helpers for copying from/to container atomic.

  [1]: https://s3.amazonaws.com/clickhouse-test-reports/json.html?REF=master&sha=8420ce5c332f5cad97c804d2be9f8a7ba7366588&name_0=MasterCI&name_1=Integration%20tests%20%28release%2C%206%2F6%29&name_1=Integration%20tests%20%28release%2C%206%2F6%29