`--nocleanup` should provide a way to preserve test data, but should not have an impact on whether nodes are to be stopped after the test execution.
In particular, when currently running RPC tests with `--nocleanup`, then it may result in several active `bitcoind` processes, which are not terminated properly.
The environment is prepared by the main thread to guard against invalid locale settings and to prevent deinitialization issues of Boost path, which can result in app crashes.
The scope of `std::locale::global` appears to be smaller than `setenv("LC_ALL", ...)` and insufficient to fix messed up locale settings for the whole application.
dexX7