Can not validate certificate
Since the usage of msys2 and cx_freeze (rb8ab53be7a43) to build the windows client, the client can no more validate SSL certificate from the OS.
This is because the msys2 build of the ssl module skip the load of windows cert store if it was compiled with GCC (see load_default_certs of ssl.py) and instead it relies on the bundled certificate define in the OPENSSLDIR ('/mingw32/ssl' from `openssl version -d`). Of course this directory does not exist when the client is frozen and so no standard ca certificates are load.
I propose to copy the ssl directory from msys2 (which comes from the mozilla project https://github.com/Alexpux/MSYS2-packages/blob/master/ca-certificates/PKGBUILD) and to set the environment variables SSL_CERT_FILE and SSL_CERT_DIR by default to the ssl directory. This way, administrator who wants to use a different paths can set the variables globally and the user can still put a ca_certs file in its configuration directory.